CA2084993C - Unstretched synthetic papers and methods of producing same - Google Patents

Abstract

Novel, unstretched synthetic papers being virtually free of mechanically produced microvoids and having a porous surface for writing and printing thereon are disclosed. The unstretched synthetic papers of the instant invention are formed typically by extruding from pellets a film or sheet material formed with a continuous olefin resin matrix containing an effective amount of a particulate filler having microvoids inherent thereto, such as a diatamaceous earth. The microvoid particulate filler is dispersed somewhat uniformely yet randomly throughout the continuous olefin resin matrix of the unstretched synthetic papers to provide non-mechanically produced microvoids in with the surfaces porous for imparting writeability and printability thereto. The novel, unstretched synthetic papers of the present invention have good receptivity and retentivity for common writing materials, such as ink, pencil lead, and paint, even though they are not mechanically stretched to form mechanically produced microvoids .

Description

WO 92/00188 PCr/US91/04368 ~ 208~9~3 ~
l~ PAPER8 AND
ME~T~OD8 OF ~ _ 8AMB

Fioll~ of th~ ~nvontion The present invention relates to an ul~LL~tc ll~d synthetic paper-like film which is virtually free of ` An; ~rAl ly ~LU-Iu~:d microvoids and 5 formed with a continuous olefin resin matrix containing a particul~te filler having pre-existing microvoids provided therewith f or providing microvoids in ~ r~tion with a surface of the synthetic paper-like film for imparting writeability and 10 printability thereto. Unstretched synthetic papers of the instant invention are suitable for use as, for exa~ple, writing paper, envelopes, in-mold labels, p~esr.uL~ scnsitive labels, tape, ~ags, cups, wrappers, poster paper, cards, packaging paper, labels, greeting 15 cards and the like.

B~ckqround Conventional writing paper is typically formed of a thin layer of interrhAngp Ihle cellulosic WO 92/00188 - - ^ PCr/l~S91/04368 . 1. 2084993 ~ ~
fibers and i5 ~ u~cd from raw materi~ls such as wood, pulp, textile fibers, waste materials and waste paper. One major drawback associated with conven-tional writing paper is its low physical ~L~ yL1~ when wet. This is believed to be attributable to the Ahun~lAn~ e of hydroxyl groups in the cellulose which imparts ~L~ rl wetability to the paper when exposed to, for example, water. In addition to this disadvantage, the cost of generating pulp for conven-tional writing paper has dramatically increased over the years.
In view of these drawbacks, numerous attempts have been made in the industry to produce paper substitutes from synthetic materi~ls such as synthetic resins. Although various synthetic olefin resins, such as polyethylene and polypropylene, have been plL,yosed as the bases for paper substitutes, the surfaces of such olefin resins are inherently hydro-phobic and non-polar, resulting in poor or inadequate receptivity to common writing and printing materials such as inks, pencil leads, paint and the like.
Attempts to improve the ink-receptivity of such olefin resins by the addition of polar fillers, for example, have been l~ncllrcpcsful by reason of the fact that relatively small amounts of such fillers are believed to be inef fective since they remain totally encapsu-lated by the olefin resins and thus the surface of th~

2 0 8~ PCr/US91/04368 sheets still pre~ient an overall h- , non-polar surface. Large amounts of such fillers, on the other hand, are believed to result in a deterioration of the desired physical properties, such as flexibility, tear 5 resistance, tensile ~LLe.-~L}l, etc., to the point where the filled olefin resins are no longer useful as paper substitutes .
In attempts to overcome these def i c; ~nri~-c, the industry has resorted to a variety of elaborate 10 and ~ 1 ic?.ted methods to produce synthetic papers.
For example, U.S. Patent No. 3,775,521 ~i~crlo5~c a thermoplastic synthetic paper in the form of a cellu-lar multi-layer film formed by biaxially stretching a thermoplastic sheet -' of an olefin resin, a 15 styrene resin and an inorganic filler. IJ.S. Patent No. 3,775,521 teaches that in order to impart write-ability and printability, it is critical to mechan-ically treat the synthetic papers , i . e ., to stretch the synthetic papers, to generate mechanically pro-20 duced microvoids. For examples of other syntheticpapers which rely upon -h~nic~l processing, i.e., stretching, to produce microvoids to impart write-ability and printability thereto, see U.S. Patents, No. 4,705,71g, No. 4,359,497, No. 4,340,639, No.
4,318,950, No. 4,151,159, No. 4,097,645, No.

3,922,427, No. 3,903,234, No. 3,855,056, No.
3,841,943, No. 3,840,625, No. 3,790,435, No.

WO 92/00188 PCr/US91/04368 20~4~9~ _4_ O
3,783,088, No. 3,551,194, No. 3,765,991, No.
3,758,661, No. 3,738,904, No. 3,551,538 and No.
2,971,858.
As an alternative to - -n;r~lly stretching 5 the synthetic papers to produce microvoids, U. S .
Patent No. 3, 840, 625 ~;~U 1~P: a method which relies upon elution and coagulation to deposit fine porous structures on the exterior surface to generate a paper-like film which can be used as a paper substi-tute. More particularly, U.S. Patent No. 3,840,625 provides a process for producing a synthetic paper by first forming a film consisting essentially of an ethylene synthetic resin, a styrene resin and an inorganic filler, followed by dissolving the styrene resin with a first liquid and then precipitating the dissolved styrene resin with a second liquid to deposit the precipitated styrene resin onto the surface of the treated film. For other examples of synthetic papers which are ~ormed ~y elution, see U. S .
2o Patents, No . 3, 855, 056 and No. 3, 551, 538 .
As another alternative method, U.S. Patent No. 4, 097, 645 discloses a synthetic paper formed by coating a previously stretched olefin resin film containing a filler with an ethylPnP;m; nP adduct of a polyaminepolyamide for improving ink adhesion. For examples of other coated synthetic papers, see U . S .
Patents, No . 4, 705, 719 and No . 4, 340, 639 .

WO 92/00188 PCr/US91/04368 ~ _5_ 20~
In yet another alternative method, U.S.Patent No. 3,922,427 discloses a :-LL~t-l-ed synthetic paper-like film onto which an ethylenically unsatur-ated carboxylic acid, its anhydride, ester or amide 5 has been graft copolymerized to produce a synthetic paper .
In still a further alternative method, U.S.
Patent No. 3,841,943 tlicr~os~c a synthetic paper produced by laminating a paper-like film formed with a 10 th~ tic resin and an inorganic filler onto a previously stretched thermoplastic film, and then stretching the laminate.
In still a further alternative method, U.S.
Patent No. 3,553,302 discloses a syr.thetic paper 15 produced by hydrating a sheet formed with a polyolefin resin containing gypsum, calcium sulfate hemihydrate and soluble anhydrite to impart printable properties to the f ilm .
In addition to the above-described methods 20 for producing synthetic papers, there are still other methods for obtaining synthetic papers. For example, a synthetic resin can be formed into staples or filaments which are interentangled and thus ~Lc,-luced into a thin synthetic paper, as in the case of conven-25 tional pulp paper. Foamable styrene resins can beextruded into a thin sheet form to obtain a paper-like foam styrene resin film. Synthetic papers can also be WO 92/00188 ~5 PCr/US9l/04368 obtained by flowing and spreading a solvent-dissolved synthetic resin onto a f ilm to obtain a multi-c~ r surface-ru~.Jl- ~d paper-like film. Still further, synthetic papers can be ~ ~ u-luced by coating the 5 surface of a synthetic resin film with an inorganic or organic filler with the use of a binder or by embed-ding the same by means of heat and pressure. Alterna-tively, there are methods for obtaining synthetic papers by ron~h~n; ng the surface of synthetic resin 10 films either by treating the surfaces with solvents or by treating them electrically, rhDmic~l ly and/or n;c~lly.
While paper-like th~ ctic synthetic resin f ilms obtained by such known methods may possess 15 certain favorable properties, such as water resis-tance, as compared with conventional paper made from pulp, their printability and paper-like properties are not only sometimes unsatisfactory, they may even change with the passage of time due to the complex 20 manufacturing processes used to produce such paper-like films. Regardless, even if the paper-like films produced heretofore do not loose their favorable properties, they nevertheles~ are expensive to produce as a result of the complexities, additional ~ L~;
25 and additional processing steps associated with the manufacturing processes utilized hitherto to produce the synthetic paper substitutes.

~ -7- 2~4593 Consequently, there is a demand in the industry for a synthetic paper substitute which has a wide range of utility and good paper-like characteristics including good receptivity and retentivity for writing materials, such as ink, pencil lead, paint and the like. Moreover, there is a demand in the industry for a synthetic paper substitute which can be manufactured simply and inexpensively.

Summary of the Invention In brief, the present invention alleviates the above-mentioned disadvantages and shortcomings of the present state of the art through the discovery of novel, unstretched synthetic papers for writing and printing thereon.
~ he present invention provides a synthetic paper consisting essentially of a continuous olefin resin unstretched matrix without an ethylene/vinyl copolymer accomodation resin substantially free of mechanically produced microvoids for writing and printing thereon, the continuous olefin resin matrix having uniformly dispersed therein an effective amount of ~iller particles having microvoids, the dispersed sd/~

-7a- 208499~
particles being exposed at a surface of the paper, the filler particles having microvoids at the surface for receiving and retaining ink or similar imaging material in the microvoids thereby imparting writeability and printability to the synthetic paper.
Generally speaking, the unstretched synthetic papers of the instant invention, which are substantially free of mechanically produced microvoids, are formed with a continuous olefin resin matrix containing an effective amount of a particulate filler having pre-existing microvolds provided therein. The microvoid particulate filler is dispersed throughout the continuous olef in resin matrix of the synthetic papers of the instant invention to provide microvoids in communication with the surfaces of the synthetic papers for imparting thereto receptivity and retentivity for common writing and printing materials, such as ink, pencil lead, paint and the like.

sd/ ~

WO 92J00188 - PCr/~JS9l/04368 ~ 20849~3 ,, The synthetic papers according to the present invention have excellent 6~iffnocs~ tensile n~L~I~yLh~ and flexibility a6 are required for paper materials, they are generally uniform in th;rt~noss~
and they have good tear resistance and writeable and printable properties. The synthetic papers of the instant invention, unlike those provided heretofore, rely upon the presence of microvoids inherent to and thus provided by the particulate filler located at their surfaces to impart the good writeable and printable characteristics thereto. These surprising characteristics are believed to occur since the microvoid particulate filler, which is integrally formed within the continuous olefin resin matrix, is dispersed somewhat uniformly but randomly there-thLUuylluuL SO that the non ~- -nicAlly ~ duced microvoids are provided at the surfaces of the syn-thetic papers to render such surfaces porous for imparting writeability and printability thereto.
Moreover, these surprising writeable and printable characteristics are amazingly accompl`ished even though the synthetic papers of the instant invention are not nirAlly stretched to generate mechanically produced microvoids. Thus, it has now been discovered that the added step of -hAnicAlly stretching as required heretofore to impart writeability and print-ability is no longer ner~CcAry to produce a synthetic WO 92/00188 PCr/US91/04368 ~ 9 2~9~ -paper h21ving good writeable and printable charac-teristics. In other words, the present invention has now made it pos6ihl~ to produce a synthetic paper having good writeability and pri ntAhi 1 i ty without 5 having to rely upon Anit Al ly stretching the synthetic paper to g~JIe:L~te ~- An;cAl ly ~u-lu~
microvoids to impart writeability and printability thereto .
A method for producing the synthetic papers 10 according to the instant invention provides for ~m;Y;n~ the constituents into, for example, a homoge-neous blend in the form of a pellet and extruding the pellet - into a continuous olef in resin matrix in the form of a film or sheet having a thi' kn~cs of about 1 15 mil to about 10 mils or more for making the paper-like products. Generally ~ Akin~, the olefin resins which can be used include, for instance, polyethylene, polypropylene, copolymers and the like. The microvoid particulate fillers which are suitable for use include 20 for example, dia~Am~-eo~ earth, volcanic ash, silica gels, styrogels, porous glass beads or other such equivalents. The continuous olefin resin matrix may also include other additives for achieving desired properties. For example, the continuous olefin resin 25 matrix of the synthetic papers of the instant inven-tion may include a foldability improving agent, such as a styrene resin, in a specific content. ~y -lO- 20~4993 O
il.LLudu~ ing the styrene resin into the cnntinllnll~
olefin resin matrix, the foldability of the instant synthetic papers is believed to be i uv~d. More-over, by the addition of a styrene resin into the continuous olefin resin matrix, it is believed that the synthetic papers of the present invention acquire the appearance of being multi-layered which is common-ly associated with conventional pulp writing paper.
The uni~aue and surprising writeable, print-lO able and paper-like properties associated with the synthetic papers of the present invention are amazing-ly accomplished without having to resort to expensive and complex r~ nicll ~ rhPmic~l and electrical processes as done by the industry heretofore. Accord-15 ingly, when following the t~ hingc of the instantinvention, m-nllfact~rers of paper substitutes are no longer required to mechanically stretch the synthetic papers formed with olefin resins to generate mechan-ically produced microvoids for imparting writeability 20 and printability thereto, since the paper substitutes of the instant invention can be formulated with a continuous olefin resin matrix which includes an effective amount of a particulate filler having pre-existing microvoids inherently formed therein for 25 providing microvoids at or on the surfaces thereof for imparting writeability and printability thereto.

WO 92/00188 PCrJUS9l/04368 -11- 2~
The novel paper substitutes of this inv~n-tion are ~qpeci:~lly suitable for use as writing paper, envelopes, in-mold labels, bags, cards, CUp8, poster paper, tape, packaging paper, overwraps, greeting 5 cards, labels and the like. When the novel synthetic papers of the instant invention are used as in-mold labels for plastic articles, such as plastic bottles, produced by blow-molding terhniqn~c, they uniquely afford cost saving and convenient advantages by 10 permitting the plastic articles with such in-mold labels positioned thereon to be recycled. When the novel synthetic papers of the present invention are used as writing paper, envelopes, greeting cards, labels, tape, ~V~LWLllyS, cards, poster paper, pack-15 aging paper, cups, bags, etc., they also afford costsavings and convenient advantages to the manufacturers thereof due to, among other things, the simplified technique for manufacturing such synthetic papers.
Moreover, since it is not n~-r~-C_~ry to subject the 20 novel synthetic papers to solvent, chemical or elec-trical treatment, they will not generally split, crack, deform or lose their desired properties over time .
The present invention therefore now makes it 25 possible to produce a synthetic paper which surpris-ingly exhibits good paper-like ~ualities including good receptivity and retentivity for common writin--2 ~ ~ 4 9 ~, 3 = Pcr/US91/04368 materials, such as ink, pencil lead, paint and the like, without resorting to expensive and elaborate ~- 9nir~1~ rhQTn~c~l and electrical ~-mlfactllring tQ~hn;q~Qs required heretofore. It should therefore 5 now be apparent to those versed in this f ield that certain of the problems attendant with synthetic papers provided hitherto are uve~ ~ in a relatively simple, yet unobvious manner by the present invention.
~he above feal_uL_s and advantages of the 10 instant invention will be better understood with reference to the ..,~ nying figures, detailed description and example. It should also be understood that the particular paper substitutes illustrating the instant invention are ~9ry only and not to be 15 regarded as limitations of the invention.

Brief Description of the Fiqs.
Reference is now made to the a~ ,onying Figs . in which certain Figs . illustrate ` ' i - ~s of 20 the present invention from which its novel features and advantages will be apparent:
Fig . 1 is an exploded view magnif ied by 5,000X of diatamaceous earth particulate filler particles having pre-existing microvoids inherent 25 thereto which can be utilized in the instant inven-tion;

WO 92/00188 PCr/US91/04368 -13- 2~8~993 Fig. 2 is an ~Yplo~rl view ~n;fi~c'l by 5, OOOX of a portion of a surface of an u.-~LL~L.,l.ed synthetic paper-like film p~uduced with dia~r~c~ou~
earth particulate filler particles having pre-existing 5 microvoids inherent thereto in accordance with the instant invention, which illu~LLc,tes such a particle on or at the surface thereof for imparting write-ability and prin~ability thereto;
Fig. 3 is an exploded view r-7n; fied by 10 5, OOOX of a portion of a cross-section of an un-stretched synthetic paper-like film p~c duc~d in accordance with the instant invention illustrating diatamaceous earth particulate filler particles having pre-existing microvoids inherent thereto which are 15 dispersed thereth~uus~l.uuL, as indicated by a sponge-like texture:
Fig. 4 is an exploded view magnified by 5, OOOX of calcium carbonate particles which appear to be devoid of any pre-existing microvoids;

Fig. 5 is an exploded view magnified by 5, OOOX of a portion of a surface of an unstretched plastic film formed with calcium carbonate particles devoid of microvoids, which illustrates such a parti-cle on or at the surface thereof: and Fig. 6 is an exploded view magnified by 5, OOOX of a portion of a cross-section of an un-stretched plastic film formed with calcium carbonat~

WO 92/00188 2 0 8 4 9 9 3-- PCr/US9iio4368 pnrticles devoid of microvoids which ar~ dispersed therethL uuylluu L .
D~tnile~l De~cription By way of illustrating and providing a more complete appreciation of the present invention and many of the attendant advantages thereof, the following detailed description is given cnnr~rning the novel unstretched synthetic papers and methods of producing same.
The synthetic paper-liXe products of the instant invention can be 1~ uduced by a process com-prising melt mixing and forming a h~: j n~ol~c blend comprising an olefin ~esin in an amount by weight of about 60% to about 90% and a particulate filler having pre-existing microvoids provided therewith in an amount by weight of about 10% to about 40%, and thereafter shaping the melt mixed h~ blend into a film or sheet having a continuous matrix. The microvoid particulate filler is dispersed somewhat uniformly but randomly throughout the continuous matrix such that microvoids are provided in i r~-tion with the surface for imparting writeability and printability thereto, as illustrated in Figs. 1-3.
Once produced, the film or sheet can be written or printed on, adhesive coated on one side thereof if desired, and die cut. By the phrases "particulate WO 92/00188 PCr/US91/04368 -15- 2 ~ ~
filler having microvoids" or "microvoid particulate filler, " they are used in a broad sense herein and refer to any organic or inorganic substance in the form of particles having microvoids for imparting 5 porosity, such that when the particulate filler is blended into the continuous olefin resin matrix, the particulate filler provides microvoids at, on and/or near the surfaces of the unstretched synthetic films or sheets produced to impart writeability and print-10 ability thereto, as depicted in Figs. 1-3. Neverthe-less, it should be understood that the terms "par-ticulate filler having microvoids" or "microvoid particulate filler" are also intended to include any organic or inorganic substance which has the ability 15 to impart effective porosity to at least the surface of an unstretched synthetic f ilm or sheet produced in accordance with the t~Arh;n~ of the instant invention to impart acceptable writeability and printability thereto. The terms "particulate filler having micro-voids" or "microvoid particulate filler" are not meant, however, to include those fillers which are incapable of imparting porosity to the surface of the f ilms or sheets produced for imparting good write-ability or printability thereto, such as particulate fillers virtually devoid of microvoids and formed of nù..~u~uus materials, like calcium carbonate, as illustrated by Figs. 4-6.

WO92/00188 20849~3 -- PCI/US9l/04368 By the term "microvoid" as used herein in the abuv_ pl.Lases, it too is used in a broâd sense herein and refers to voids smaller than about 20 microns, but nevertheless of any sufficient size for 5 receiving and retaining writing materials for imparting writeability to the surfaces of the syn-thetic papers of the present invention. See for example the particulate f iller depicted in Fig . 1, as compared to the particles illustrated in Fig. 4.

Examples of microvoid particulate fillers that can be used in the instant invention include diat~r--e-nlc earths, volcanic ash, silica gels, styrogels, porous glass beads and the like. ~Y~ c of diatamaceous earths that may be dispersed within the continuous olefin resin matrix of the synthetic paper-like films of the instant invention include Eagle-Picher's Celaton~MW-21, MW-25 and MW-27, Witco's Micro-Ken 801, and John Manville's Celite~212. An example of volcanic ash that may be utilized with the present invention is Grefco Inc. 's Perlites' material, such as FFl~and FF26~ Regardless of which microvoid particulate filler is selected, it should be under-stood that the microvoid particulate filler should have the properties defined above so that when dis-persed throughout the continuous olein resin matrix of the paper-like product in ân effective amount, an effective amount of microvoids are in communication ~ ~R~e-m~k .

-WO92/00188 PCr/~S91~04368 ~ -17- 2 0 ~
with the surface to impart writeability and print-ability thereto. The amount of microvoid particulate filler to be used will of course be influenced by the 5ize of the particles, the type of olefin resin 5 5elected, the amount of other 2dditives used, the molding conditions, the thi~-kn~cc of the film produced and the like, but generally, such particulate fillers are used in an amount of between about 5% and about 30% by weight. ~ypically, the microvoid particulate fillers have a particle size in the range of between about 2 microns and about 20 microns, and preferably between about 5 microns and about 10 microns.
The olefin resins that can be used in the instant invention are, for example, high density poly-ethylene, medium density polyethylene, low density polyethylene, ethylene-vinylacetate copolymers, ethylene-propylene copolymers, polypropylene, poly-butene-l and the like. Such olefin resins may be used individually, or in combination. High density poly-20 ethylene is F-crPci~l ly preferred and examples thereof include those available through Dow Chemicals, HDPE
(10062) and Quantum Chemical HDPE (6206).
According to the present invention, it may also be desirable to add other additive resins to the above-mentioned composition. For instance, when a styrene resin or the like is used as the additive resin, good printability, stiffness as well as WO 92/00188 2 0 8 4 9 9 3 Pcr/US91/04368 foldability is imparted to the synthetic pApers. It is believed, however, that good foldability typically is not obtained with a styrene re5in content of less than about 5% by weight. On the other hand, it is 5 believed that the styrene resin content should not be greater than about 10% by weight in order to prevent substantial lowering of the tear -LL~::IIY~, impact strength and tensile strength of the synthetic papers produced therewith. Examples of styrene resins that l0 can be used in this invention include poly~LyLene, poly-alpha-methylstyrene, styrene-butadiene copolymers having a high styrene content, high impact poly-styrene, acrylonitrile-butadiene-styrene copolymer, acrylonitrilc ~yl~=ne copolymer, :.~yL~llC - ~hylene-15 methacryate copolymer and the like. When copolymersof styrene with other monomers are selected, it is believed that the styrene content should be at least about 50%. An example of a polystyrene resin that can be used in the instant invention may be obtained from 20 Dow Chemicals under the trademark Styron 420 or from Phillip under polystyrene resin.
In this invention, an inorganic filler may be further added to the mixture of the olefin resin and microvoid particulate filler with or without the 25 above-mentioned additive resins, such as a styrene resin. As to the inorganic filler, talc, kaline, zeolite, mica powder, asbestos powder, calcium WO 92/00188 PCI/US9l/04368 -19- 2f~8~9?~
carbonate, r-gn~sillm carbonate, calcium sul~ate, clay, silica pOwaer, aluminum magnesium sulfate, barium sulfate, zinc sulfite, titanium oxide, zinc oxide and the like may be used. When an inorganic filler is 5 selected, it i5 preferred that such inorganic filler have an average particle size of less than about 10 microns, and more preferably less than about 5 microns . The inorganic f illers can be used in amounts of between about 0 and about 20% by weight, and 10 preferably between about 59~ to about 10% by weight.
Among such inorganic fillers, calcium carbonate is particularly preferred and may be obtained from ECCA
Calcium Products, Inc., Supercoat, Georgia Marble, Gamma Sphere~CaCO3, and Pfizer, multi-flex MM coated 15 and uncoated CaCO3. While calcium carbonate is a preferred inorganic filler, it should be appreciated that it is not to be used as a substitute f or the microvoid particulate filler to impart writeability to the surfaces of the paper-like films of the instant invention since calcium carbonate particles are generally devoid of the n~ C~s~ry microvoids, as illustrated by Figs. 1-6.
For the purpose of improving moldability of the composition and physical properties of the resul-tant film and increasing the amount of the particulate and/or inorganic filler in the composition, it is believed that natural rubber or synthetic rubber such ~ 7~e-rne~k wo 92/onl88 2 Q 8 4 9 9 3 PCI/US9i/04368 a8 polyurethane rubber, ~LYL~II~ buLadiene rubber, acrylonitrile-butadiene rubber, poly-butadiene rubber, polypropylono-~Yi~o rubber and the like may be added to the continuous olefin resin matrix. Such rubber, 5 however, should not be used in an amount which exceeds the total amount of the olef in resin, any additive resin, such as a 6tyrene resin, and/or the particulate filler. If an additive resin already containing rubber, such as high impact polystyrene, is used, this lO should be considered when adding other rubber con-taining materials to the composition.

In the present invention, the synthetic papers may be pigmented to impart desirable aesthetic qualities by for example incorporating into the 15 continuous matrix a colored or white pigment, such as titanium oxide. In addition to being pigmented, it i5 also possible to further add other various additives to the synthetic papers such as a plasticizer, a stabilizer or other similar agents. Further, for 20 promoting the dispersion of the particulate filler and/or inorganic filler, it may be advantageous to use a surfactant, a dispersing agent or other similar agent. It is also possible to add an ultraviolet ray absorbent or an anti-oxidant so as to improve weather-25 ability of the resultant structure, or to add ananti-static agent. These types of additives would be -21- 2~8~g3 employed in their customary amounts well known to those versed in this f ield .
The above-mentioned specif ic compositions are typically melt mixed sufficiently by means of, for 5 example, a mixing roll, a Banbury mixer, an extruder or the like, and then molded into a film or sheet by means of, for example, a calendar roll, an extruder or the like. Generally, the molding is performed in a manner such that the resultant f ilm or sheet product 10 has a continuous olefin resin matrix with a ~hirknegs of between about l mil and about lO mils, and pref-erably between about 4 mils and about 6 mils.
When a product of the present invention is ~L.,~uced as described above, a :~LLU~;LULC: having the 15 appearance of multi-layers may result due to the fact that when an additive resin is blended into the composition, the resultant product has a tendency of sometimes undergoing separation of the olefin resin from the additive resin, such as a styrene resin, to 20 create the appearance of a multi-layered-like struc-ture which is characteristic of conventional pulp paper. As a result, a paper-like product produced in accordance with the instant invention has the charac-teristics of being stiff and foldable, and it can be 25 torn. In addition, when a styrene resin is utilized, it is believed that various layers may be peeled from the paper-like products produced in accordance with the instant invention which is further characteristic of conventional pulp paper.
The synthetic paper-like structures of the in6tant invention can be formed into films or sheets which can be 5 printed, adhesive coated, and die cut into plastic labels or used as in-mold plastic labels for plastic article6, 6uch as bottle6, produced via a blow-molding operation or the like. The use of the paper-like products of the in6tant invention a6 pla6tic in-mold label6 ha6 many ~dvantages over 10 paper labels. In particular, when the paper-like products of the instant invention are u6ed a6 pla6tic in-mold label6, the label6 and pla6tic article6 to which the in-mold label6 are applied can be ea6ily and advantageou61y recycled. When utilizing the 6ynthetic paper-like product6 of the pre6ent 15 invention a6 in-mold label6, they may be applied to pla6tic bottle6 in accordance with technique6 well known to tho6e ver6ed in the art, 6uch a6 tho6e de6cribed in U. S. Patent6, No. 4,708,630, No. 3,108,850, and No. 3,417,175. In addition, the 6ynthetic paper-like product6 of the in6tant 20 invention have many other useful applications including writing paper, envelopes, tape, greeting cards, overwrap, bags, packaging paper, labels, cards, poster paper, cups, etc .

~C

WO 92/OOt88 PCr/US91~04368 -23- 2~
Examples of a paper substitute of the present invention will now be further illustrated with reference to the following 5 Example I - 8ynth~tic Paper An unstretched synthetic paper-like product free of mechanically produced microvoids and formed with a continuous olefin resin matrix which includes an effective amount of a particulate filler having lO pre-existing microvoids, wherein the microvoid par-ticulate filler is somewhat uniformly dispersed throughout the continuous olefin resin matrix for providing n.,~ nically produced microvoids in communication with a surface of the paper-like product 15 for imparting writeability and printability thereto, is produced by mixing one of the following two compo-sitions into a ~ eous blend and shaping the blend into pellet form:
Composition I By Weiqht 20 High density polyethylene About 62%
Poly ~ Ly L ~lle 1~ 7 %
Calcium carbonate " 7%
Diat~r--eol~c earth " l996 Titanium oxide " 5%
Composition II By Weiqht High density polyethylene About 71%
Polystyrene " 8%
25 Calcium carbonate ~ 5%
Diatamaceous earth " 10%
Titanium oYide " 6%

WO 92/00188 c~ -24-Upon mixing one of the above recited Compo-sitions to form a homogeneous blend and shaping the blend into a pellet, the pellet is extruded with for example a conventional single screw extruder into a 5 film or sheet having a continuous olefin resin matrix and a thickness of between about l mil and about lO
mils, and preferably about 4 mils to about 6 mils.
The resulting unstretched synthetic paper-like product exhibits excellent receptivity and retentivity for lO common writing materials, such as ink, pencil lead, paint and the like, when it is written or printed on the surface thereof. Surface primers may be applied prior to printing to enhance printing. Protective coatings, such as a lacquer, may also be applied after 15 printing to protect the printed surface from moisture, abrasion, etc. In addition, the unstretched synthetic paper-like product exhibits excellent paper-like and foldability characteristics. I'hese properties are surprisingly accomplished without stretching the 20 extruded synthetic paper-like product.

Ex mple II - In-Mold Labels Using Composition I as recited in Example I, the homogeneous blend is extruded through a die to 25 produce a flat~sheet or film having a controlled thickness, typically of about 4 mils In addition to extrusion, the film can be blown or cast, embossed, WO 92/00188 - ~ PCr/US91/04368 2~9~3 matte or ~lat. In a further operation, a suitable heat activatable adhesive is applied or coated onto one side of the film. The adhesive is such that the adhesion properties are activated in a subsequent blow molding operation during application of the in-mold label to a plastic container. On the opposite side of the film, a decorative pattern is applied thereto, normally by printing, to provide a label design and information required for the finished article, such as a bottle or container. The printing can be done by various methods including roto~L~Ivul~, offset, flexo-graphic and the like. Surface primers may be coated onto the f ilm prior to printing . Protective coatings, such as a lacquer, may be applied on top of the printing to protect the printing from moisture, abrasion, etc. The film is then die cut, used as label stock in an in-mold Iabel application. In the case of offset printing, the adhesively coated film may be f irst cut into sheets, then printed, and finally die cut into ~individual labels. For roto-gravure printing, the film is sheet and die cut after printing. After die cutting, the film is then in the proper shape and size for the final label.
The finished labels are applied to the bottle or container during the in-mold labeling operation. This process involves directly applying a label inside of the mold during the blow molding WO 92/00188 2 0 ~ 4 9 9 3 PCI/US91/04368 operation which forms the bottle or container. The molten plastic extruded into the mold contacts the label strategicaily positioned within the mold and in particular the adhesive side thereof as well as the 5 mold wall, at which point the molten plastic solidi-fies to form the f;niqhed article. The heat from the molten plastic activates the adhesive on the film and forms the bond between the bottle or container and the f ilm .
The in-mold labels of this Example are believe to perform equally as well as equivalent paper-based products, with the added advantages of:
l. ) the in-mold labels may match the thermal charac-teristics, i.e., melting temperature, shrinkage, heat 15 capacity, etc., of the blow molded plastic bottles or containers; and 2 . ) scrap mo~ ded bottles or containers formed with the in-mold labels of this Example may be easily recycled due to the fact that the in-mold labels are formed with materials similar in nature to 20 those utilized to form the bottles or containers.
Moreover, because the in-mold labels of this Example are formed with materials similar in nature to those utilized to form bottles or containers, the conformity problem due to shrinkage normally associated with 25 paper labels is substantially, if not totally, elim-inated. As a result, the overall product performance during use of the bottles or containers is believed to WO 92/OOt88 PCr/US9l/04368 ' ! -27- 2~8~3 be greatly ~nhAnr-~cl by use of the in-mold labels of this invention.
Ex ple I}I - PL~ -a~ LC 8ensitive Lllbels The Composition II as recited in Example I
is used in this Example III to formulate pressure sensitive labels. A h 3-~n-~ollq blend of Composition II is extruded into a uniform film having a controlled thickness, generally of about 4 mils . This f ilm is believed to have excellent printing characteristics similar to the films of Example II, but has enhanced properties in terms of an increase in tear strength and toughness and a decrease in stiffness. In a further step, the produced f ilm is coated with a pressure sensitive adhesive laminated to a release liner and die cut to produce ~L~::SaULe sensitive labels. The pressure sensitive adhesive is believed to retain its adhesive nature at room temperature and, as such, the release liner such as silicone coated paper can be applied to the film before rewinding it into rolls. Normally, these rolls are slit down to the finished widths of the pressure sensitive labels.
The slit rolls are then normally strate-gically printed thereon with a decorative pattern and/or product information. The printing can be done by various printing methods suitable for roll stock, such as flexographic, rotogravure, and others.

WO 92/00188 ,~ 2 o ~ ~ ~ 9 ~ PCI /US91/04368 -28- ~D
Surface primers may be applied prior to printing to enhance printing. Protective coatings, such as a lacquer, may be applied after printing to protect the printed surface from moisture, abrasion, etc.
The printed, adhesive-coated film can then be die cut into the finished shape of the pressure sensitive labels. This is typically down with a rotary or single die cutting unit. The cut can be made through the single layer of film without cutting through the release paper. To achieve this, the film usually has a balance of properties, mainly between tensile and elongation properties. This is generally achieved through the materials used in the f ormu-lation. After die cutting, the film is again rewound into rolls and stored until further processing.
The pressure-sensitive film labels can then be transferred to bottles or containers or the like by peeling or removing the labels from the release liners and, with pressure, properly applying the labels to the appropriate bottles, containers or the like. In modern, high speed filling lines, this is normally done in line by unwinding the film rolls, moving the films in line near the bottles, containers or the like, peeling the labels from the release liners, and transferring the peeled labels to the bottles, con-tainers or the like. All of the above can be done mechanically in line. Such pressure sensitive labels WO 92/00188 ; PCI/US91/04368 -29- 2084,~3 should have the proper balance of stiffness and flexural streng~ch to perform adequately in this operation. It is believed that the combination of good printability and the balance of stiffness and tear strength make the films of this Example especial-ly suitable for pressure sensitive label applications for, inter alia, plastic bottles, containers and the like .
Example IV - Envelopesl and Baq~
Composition I as recited in Example I is f ormed into a homogenous blend and extrud=ed through a die to produce a flat sheet of film of controlled thickness for formulating a plastic, printable enve-lope. For this application, a coextruded film is generally needed to provide different properties on each side of the film. Typically, one side of the film is the printable side made with the printable formulations identified by this invention and in particular Composition I as recited in Example I. The other layer provides toughness and good heat sealing properties and could be composed of a material such as a linear low density poIyethyLene having a melt index of about l. 0 . A coextruded film of this type can be produced by any of several coextrusion methods well known in the industry.

WO 92/00188 2 0 8 4 9 ~ 3 PCI`/US91/04368 One such coextrusion method includes feeding the different materials into two different extruders and then combining the flows from the extruders at the die in such a manner as to form two distinct uniform layers. More particularly, a hl , -IOUS blend of Composition I recited in Example I is coextruded into a two layer film, with the second layer consisting of the l. O melt index linear low density polyethylene and a color concentrate, such as a white concentrate.
This coextruded film has a total thickness of about 3 . O mils . The coextruded f ilm can then be slit into a suitable width and wound into a roll. The printable side of the film is then printed by methods such as flexographic, rotogravure, etc., and then rewound into a roll. Surface primers may be applied prior to printing to enhance printing. Protective coatings, such as a lacquer, may also be applied after printing to protect the printed surface from moisture, abra-sion, etc. The printed film is then converted into an envelope or bag. This is normally done by unwinding the roll of printed f ilm, f olding the f ilm across its width, heat sealing or gluing the edge and cutting and heat sealing the envelope to a suitable length.
Normally, adhesives are applied to seal the envelope in use. Other features, such as perforation for tearing, clear exterio~=pouches, and relQase tapes may be added . The f inished product then has a printed WO 92/00188 PCr/US91/04368 -31- 2l78~9!93 _~

outside layer with decorative patterns and/or informa-tion, with an inner layer of tough, tamper resistant f ilm with high opacity to conceal the contents of the envelopes. Due to the porous nature of the outer 5 printable layer, this surface gives good adhesion to typical postage stamps, which normal plastic films available heretofore do not.
This unique combination of properties to form the composite films of this Example is believed 10 to be especially useful in applications such as shipping envelopes, overnight mail envelopes and bags.
It should be understood that the properties of these composite films, such as surface properties as coeffi- ~-cient of friction, texture and stiffness, can be ; nclc-p ~n~ tly varied for each layer as desired.

E:xample V - Anti-Static Printable Films C To form an anti-static printable film, an anti-static agent, such as Hexcel 273C or Hexcel~73E

Fine Chemicals Co., 205 Main Street, Lodi, New Jersey 07644 or Armostat~310 or Armostat~410, Armak Chemicals Co., 300 South Wacker Drive, Chicago, Illinois 30306, can be added to the Composition I as recited in Example I in convertibles of 0 .1 to about 0 . 2% by weight of the Composition I. It is believed that the anti-stat will migrate to the surface of the film to produce a surface that will readily dissipate a static ~ Ir~e~

charge, or in other terms, prevent a static build up and discharge at the film's surface. This anti-static property is believed to be benef icial in various operations such as printing, sheet cutting, label 5 application, etc., where static build up can c2use problems. In addition, it is believed that certain fillers, such as diatamaceous earth, control the migration of the anti-stat material to the surface of the film in such a manner that the printing charac-teristics or adhesion properties of the film surface are not compromised.
Thusly, it can be seen from the Examples, that the unstretched synthetic paper products produced in accordance with the instant invention are effective substitutes for conventional pulp paper and the like.
As a result, the unstretched synthetic paper products of the instant invention provide simple, but unobvious means heretofore unavailable for providing paper substitutes .
The present invention may, of course, be carried out in other specif ic ways than those herein set forth without departing from the spirit and essential characteristics of the instant invention.
The present embodiments are, therefore, to be con-sidered in all respects as illustrative and not restrictive, and any changes coming within the meaning WO 92/00188 2 Q 8 4 9 ~ ~: PCI/US91/04368 ~ .v y and equivalency range o~ the ~ppPn~!P~l claims are to be embraced therein.
Having described our invention, we claim:

Claims (14)

1. A synthetic paper consisting essentially of a continuous olefin resin unstretched matrix without an ethylene/vinyl copolymer accomodation resin substantially free of mechanically produced microvoids for writing and printing thereon, said continuous olefin resin matrix having uniformly dispersed therein an effective amount of filler particles having microvoids, said dispersed particles being exposed at a surface of said paper, said filler particles having microvoids at said surface for receiving and retaining ink or similar imaging material in the microvoids thereby imparting writeability and printability to said synthetic paper.

2. A synthetic paper as recited in claim 1 wherein said olefin resin is a high density polyethylene or polypropylene.

3. A synthetic paper as recited in claim 1 wherein said particulate filler is a diatomaceous earth .

4. A synthetic paper as recited in claim 1 wherein said particular filler is selected from a group consisting of volcanic ash, silica gels, styrogels and porous glass beads.

5. A synthetic paper as recited in claim 1 wherein said olefin resin is present in said continuous matrix in an amount of about 60% to about 90% by weight and said particulate filler is present in said continuous matrix in an amount of about 10% to about 40% by weight.

6. An unstretched synthetic paper as recited in claim 1 wherein said synthetic paper is an in-mold label for a plastic structure wherein such plastic structure is produced by blow-molding.

7. A synthetic paper as recited in claim 1 wherein said synthetic paper is in the form selected from the group consisting of a writing paper, in-mold label, envelope, card, tape, overwrap, bag, cup, pressure-sensitive label, greeting card, label, packaging paper and poster paper.

8. A synthetic paper as recited in claim 1 wherein said continuous olefin resin matrix further includes a styrene resin in an amount of 5% to about 10% by weight for imparting additional paper-like characteristics to said synthetic paper.

9. A synthetic paper as recited in claim 1 wherein said continuous olefin resin matrix further includes an inorganic filler.

10. A synthetic paper as recited in claim 9 wherein said inorganic filler is present in an amount of up to about 20% by weight.

11. A synthetic paper as recited in claim 1 wherein said synthetic paper has a thickness in the range of between about 1 mil to about 10 mils.

12. A synthetic paper virtually free of mechanically produced microvoids for writing and printing thereon, said synthetic paper being formed with a continuous matrix without an ethylene/vinyl copolymer accomodation resin comprising high density polyethylene, about 60-75%
polystyrene, about 5-10%
calcium carbonate, about 5-10%
diatomaceous earth, about 10-20%, and titanium oxide about 0-5%
wherein said diatomaceous earth is dispersed throughout the continuous matrix to provide microvoids in communication with a surface of said synthetic paper to render said surface porous for imparting writeability and printability thereto.

13. A synthetic paper as recited in claim 12, said continuous matrix comprising high density polyethylene, about 62%
polystyrene, about 7%
calcium carbonate, about 7%
diatomaceous earth, and about 19%, and titanium oxide about 5%.

14. A synthetic paper as recited in claim 12, said continuous matrix comprising high density polyethylene, about 71%
polystyrene, about 8%
calcium carbonate, about 5%
diatomaceous earth, and about 10%, and titanium oxide about 6%.