CA1238828A

CA1238828A - Composite material

Info

Publication number: CA1238828A
Application number: CA000474749A
Authority: CA
Inventors: Wolfgang Neumann; Hans-Jurgen Hendriock; Herbert Fitz
Original assignee: Hoechst AG
Current assignee: Dyneon GmbH
Priority date: 1984-02-22
Filing date: 1985-02-20
Publication date: 1988-07-05
Also published as: EP0153645A2; EP0153645B1; US4556589A; EP0153645A3; DE3563926D1; DE3444631A1

Abstract

Abstract of the disclosure:

Composite material composed of a) a plasticized PVC substrate, if appropriate a fabric coated with plasticized PVC, and b) a top layer composed of b1) 5 to 100% by weight of a mixture of an acrylic resin and plasticized PVC, and b2) 0 to 95% by weight of a fluorine-containing copolymer formed from vinylidene fluoride, hexafluoro-propylene, tetrafluoroethylene and, if appropriate, a further fluoroolefin or fluoroalkyl vinyl ether, wherein, if the content of b1) in b) is 0 to 15%
by weight, a sealing layer composed of the fluorine-containing copolymer b2) is also applied to the top layer. The composite material is particularly suitable for structural units belonging to the field of textile construction.

Description

~3

2 --The ;nvention reLates to a composite material composed of a plasticized PVC substrate which has been provided with a top layer and, if appropriate, a sealing layer.
Plasticized polyvinyl chloride is used to a large extent for surface coatings and impregnations, for ex-ample on fabrics or as an upholstery covering. It is known that, besides all their known advantages, plasti-cized PVC surfaces have the disadvantage of a somewhat 10 tacky surface, which therefore attracts soot and dust to a considerable extent, so that this property considerably reduces the value in use of the articles thus coated, above all when they are used externally. Plastic;zed PVC surfaces are therefore often provided with a so-15 called top lacquer ~finishing layer) composed of poly-acrylate resins (cf., for example, Kunststoff-Handbuch ~"Plastics Handbook"], volume II, part 1: polyvinyl chlor;de, Carl Hanser Yerlag Munich, 1963, pages 427 to 428). In order to improve the adhesion, in most cases 20 a certain proportion of the plasticized PVC or PVC paste is added. However, these PVC substrates which have been provided with a polyacrylate top layer are not completely satisfactory either. After this treatment they also tend to become soiled, even if to a slighter extent, and 25 also have an inadequate resistance to chemicals and a stab;l;ty towards weather;ng wh;ch ;s not sufficient for external use~ The polyacrylate top layer must be kept relatively thin, since top layers of this kind become sens;tive to fracture ;f the layer thickness ;s fairly 30 large and produce fractures wh;ch are vis;ble to the naked eye, and such a relat;vely thin layer ;s ;ncapable of exert;ng an absolutely complete plasticizer barrier action.
There is, therefore, a need for a suitably 35 coated plasticized PVC substrate which does not have the disadvantages ment;oned.

123~ 8 The present ;nvent;on sat;sf;es th;s requ;re-ment by means of a composite material composed of:
a) a substrate layer composed essentially of plasticized PVC, and 5 b3 a top layer, applied to one or both sides of this substrate layer and composed of:
b1) 5 to 100X by weight of a mixture of acrylic resins composed of 5 to 60X by weight of plasticized PVC
or an internally plasticized copolymer of vinyl chloride and - to bring the total up to 100X by weight, - an acry-lic resin, and b2) 0 to 95% by weight of a fluorine-containing copolymer containing 50 to 20X by we;ght of copolymerized units of vinylidene fluoride, 10 to 30X by weight of co-polymerized units of hexafluoropropylene and copolymerized un;ts of tetrafluoroethylene, the proport;on of the latter be;ng at least 30X by we;ght ;n the copolymer, and co-polymer;zed un;ts of another fluoroolef;n or fluoroalkyl v;nyl ether in an amount of 0 to SX by we;ght, subject to the prov;so that, if the content of the fluor;ne-containing copolymer b2) in the top layer is û
to 15X by weight, there is also provided, on the latter, c) a sealing layer which is solely composed of the fluorine-containing copolymer defined under b2).
The fluorine-containing copolymer employed within the scope of this composite material according to the invent,on as the component b2) of the top layer or as the seal;ng Layer possesses a number of exceptional pro-pert;es which make it suitable for use as a seal: it has a h;gh res;stance to weather;ng, o;l and chemicals; it ;s absolutely res;stant to mo;sture and prevents the m;gra-t;on of plast;c;zers through the seal;ng layer; ;t has an extremely low melt;ng po;nt or soften;ng po;nt, and, at fa;rly high contents of v;nyl;dene fluor;de (~ 30X by we;ght), it has a good solubility in organic solvents.
The last-mentioned properties facilitate the application and formation of a coherent sealing film without damage to the underlying layers of the composite material. Finally, these fluorine-containing copolymers are strongly anti-1 23~ 8 adhesive and dirt-repellent. However, whereas on their own they virtually do not adhere at all to PVC and can easily be removed again after application, they form, surpris;ngly, a f;rmly adhering bond together with the polyacrylate res;n of the top layer or on the Latter, and also do th;s if this polyacrylate resin is mixed with PVC .
The fluorine-containing copolymers employed in accordance with the invention as component b2) in the top 1û layer and/or in the sealing layer are known per se. Their preparation is effected, as described, for example, in Pelgian Patent No. 844,965, by copolymerization, prefer-ably in an aqueous suspension~ in the presence of cata-lysts which form free-radicals, such as, for example, alkali metal or ammonium persulfates. Copolymers suit-able for use as the sealing layer for the composite mate-rials according to the invention are those containing 50 to 20 X by weight of copolymerized units of vinylidene fluoride, 10 to 30 X by weight of copolymer;zed units of hexafluoropropylene and ~as the remainder up to 100% by we;ght) copolymerized un;ts of tetrafluoroethylene, the latter be;ng intended to amount to at least 30% by weight of the copolymer. The composition is preferably 45 to 3ûX by we;ght of copolymerized units of vinylidene fluo-ride, 15 to 25% by weight of copolymerized units of hexa-fluoropropylene and (the remainder up to 100X by weight) copolymerized un;ts of tetrafluoroethylene, the latter being intended to amount to at least 30X by weight of the copolymer. The sa;d copolymers can, if appropriate, also contain fa;rly small proport;ons of copolymerized units of at least one other fluoroolefin or fluoroalkyl vinyl ether, in particular perfluoropropyl vinyl ether. Copoly-mers of this type are known, for example, from U.S.
Patent No. 3,235,537 or European La;d-Open Spec;fication 2,809. The amounts of these units should not exceed 5X
by weight, preferably 3X by weight. Copolymers composed solely of copolymerized units of vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene are preferred, however.

123~8~8 In addition to other advantageous properties, if their content of vinylidene fluor;de is fairly high ( ~ 30X by weight), the copolymers thus described have a good solubility in customary organic solvents, such as, for example, methyl ethyl ketone, acetone, tetrahydro-furan, ethyl acetate or diisopropyl ketone, and also a very low - unusually low for fluorine-containing poLy-mers - melting point or melting range, which varies within the range from 90 to 180C, depending on the composition. It is therefore possible to achieve a con-tinuous and uniform coating film, either by applying such a solution and subsequently evaporating the solvent under mild conditions or by applying an aqueous dispersion and subsequently warming to 160 to 180C.
Substrates which can be used for the composite mater;als accord;ng to the ;nvent;on are sheet-like structures composed of plastic;zed poLyv;nyl chlor;de, such as, for example, sheets, f;lms, tapes and the like.
~;th;n the scope of th;s description, the term plasti-c;zed PVC ;s to be understood as meaning any type of PVC
wh;ch has been plasticized by external plasticizers, in-clud;ng also the so-called polymer;c plasticizers. It ;s also w;thin the scope of this invention for the exter-nally plasticized PVC to contain, in addition, minor pro-portions of copolymerized units of internally plastici-zing comonomers, such as, for example, vinyl acetate, acrylate or methacrylate.
Preferred substrates are fabrics and also other textile sheet-like structures, such as knitted fabrics 3û and nonwovens composed of natural fibers, such as cotton, semi-synthetic fibers, such as staple rayon or art;fi-cial silk, or fully synthetic fibers, such as polyamide, polyacrylic or, preferably, polyester fibers, which have been impregnated and/or coated with plasticized PVC.
Coated fabrics of this type preferably have a weight per unit area of 200 to 1,200 g/m2, but the amount used for coating can also be outside these limits. The plasti-cized PVC coating, in the form of a plastisol (composed of about 40 to 75, preferably 50 to 70, X by weight of 123~828 PVC and about 25 to 60, preferably 30 to 50, X by we;ght of plasticizer), ;s usuaLly appl;ed to both s;des of the textile sheet-like structure ;n at least two and not more than s;x layers, the f;rst layer on both s;des 5 conta;ning, ;f appropr;ate, an adhes;on promoter. The sa;d sheet-l;ke structure can also be composed, com-pletely or partially, of glass or other mineraL fibers.
It is also w;thin the scope of this invention to convert the plast;cized PVC completely or partially into a porous 10 or cellular structure by adding suitable auxiliaries. It is also possible to mix customary additives, such as f;llers and pigments, for example titanium dioxide, antimony(III) oxide or carbon black or stabilizers, flame-retarding agents and antistatic agents, into the 15 plasticized PVC. However, substrates which have been prepared by bonding fabrics to plast;c;zed PVC f;lms or by coextrud;ng plast;c;zed PVC w;th text;le structures, can also be employed for the compos;te mater;al accord;ng to the ;nvention. All the sheet-l;ke structures descr;bed in 20 th;s way are to be understood by the expression "substrate layer wh;ch ;s essent;ally composed of plast;c;zed PVC".
A top layer composed of b1~ 5 to 100X by we;ght of a m;xture of acrylic resins and (;f appropr;ate) b2) of 0 to 95X by weight of the fluorine-containing copoly-25 mer described above, is applied to the substrate layer onone s;de or, preferably, on both s;des. The mixture of acryl;c res;ns ;s composed of polyalkyl acrylates or polyalkyl methacrylates or mixtures thereof, this acrylic resin being mixed with 5 to 60X by weight, preferably 5 to 30 40% by we;ght, of plast;c;zed PVC or, ;n part;cular, of an ;nternally plast;c;zed copolymer of vinyl chloride. The alkyl radicals in the said polyalkyl acrylates and polyalkyl methacrylates are preferably short-cha;n alkyl rad;cals hav;ng 1 to 4 carbon atoms. Spec;al mention 35 should be made of polymethyl methacrylate, particularly preferably as a mixture with polybutyl acrylate. Without pretreatment of the substrate, these acrylic resins adhere only with difficulty to the PVC of the substrate ~ 23~ 8 layer. In order to avoid involved pretreatment stages, ;t is therefore advantageous to add proportions of, preferably externally plasticized, PVC (as has been defined above) or of internally plastic;zed PVC. The 5 latter is composed of copolymers of vinyl chloride with vinyl acetate, acrylates, methacrylates or maleates.
Additionally, b2) 0 to 95% by weight - relative to the total weight of the m;xture b1) + b2) for the top layer - of the fluor;ne-conta;ning copolymer described 1û above are incorporated ;nto th;s m;xture of acryl;c resins~
It ;s preferable to mix in 7û to 95X by weight, espec;ally 80 to 90 Z by weight - relative to the total weight of the mixture for the top layer - of the fluorine-15 containing copolymer of the component b2), the propor-tion of the mixture of b1) of acrylic res;ns then be;ng 5 to 30, and especially 10 to 20, % by weight. If the fluorine-containing copolymer b2) ;s present ;n the top layer only ;n small proportions, ~ 15X by weigh', or not 20 at all, ;t is necessary addit;onally to prov;de, on this top layer, an external sealing layer composed solely of the fluorine-conta;n;ng copolymer defined under b2). The m;xtures descr;bed for the top layer - e;ther w;th or w;thout fluor;ne-conta;n;ng copolymer - are applied from 25 organ;c solvents, such as methyl ;sobutyl ketone, methyl ethyl ketone, d;methylformam;de, cyclohexanone, ethyl acetate or tetrahydrofuran or other such solvents or m;x-tures of such or s;m;lar solvents. The amount should be about 2 to 100 g/m2, preferably 2 to 20 g/m2, and, ;f 30 appropr;ate, a deluster;ng agent is added to top layers of th;s type. Customary p;gments, f;llers or antistatic agents, such as, for example, titanium dioxide, anti-mony(III) oxide or carbon black, can be mixed into the top layer before application.
If appropriate, the fluorine-containing copolymer described above is applied, also from a solution in an organic solvent or else, however, from an aqueous disper-sion, to the sheet-like structures which have been built - up in th;s manner. The appl;cation of the top layer and, ~23~38;;~8 ;f appropr;ate, of this sealing layer, is effected by customary methods, for example by spray;ng, by roLl-coating by means of a fine screen-lined roller, by appli-cation with a doctor blade or by similar methods. The 5 thickness of the sealing layer is not critical. Even 2 9/m2 can be adequate for the sealing effect desired.
Depending on the end use, the layer appLied can have a weight per unit area of up to 20 g/m2, preferably up to 10 g/m2. Customary pigments, fillers or antistatic 10 agents, such as, for example, t;tanium dioxide, anti-mony(III) oxide or carbon black, can be mixed into the sealing layer before application.
After the application of the top layer or the sealing layer, the organ;c solvent or the water is first 15 removed by heating, and heating is then continued up to about 150 to 180C, in the course of which a cont;nuous and crack-free coat;ng film is formed. If application is made from an organ;c solvent, even heating to fairly low temperatures can also be sufficient for the formation of 20 the f;lm.
If the content of the fluorine-containing copoly-mer b2) in the top layer is more than 15X by weight, and in particular more than 70% by weight, the desired plasti-cizer barrier action, together with the other advan-25 tageous properties, is also achieved in accordance withthe invention if no sealing layer is provided.
The composite materials, according to the inven-tion, def;ned in this way possess an excellent dirt-repellency and stability to the effects of weathering, 30 oil and chemicals, and also to UV light. By virtue of this property, they are suitable for a variety of appli-cations, above all in the outdoor field and the f;eld of so-called textile construction. The following may be mentioned as examples of use of the composite mate-35 rials according to the invention: air-inflated structures, roofing webs, stressed structures, partitions, silos and the like. The following can also be manufactured there-from: tents, swimming pool linings, tarpaulins, for example for trucks, container covers and conveyor belts ~23l38;~8 and band conveyors.
The invention is ilLustrated by means of the follow;ng examples:
Preparation of the PVC substrate provided with a top layer A) The greige fabric employed is a polyester fabric composed of Trevira~ high-strength polyester yarn having the following characteristic data:
Denier (warp/weft) : 1,100/1,100 dtex 10 Ends/picks : 9/9 per cm Weave : calico - 1/1 Thickness : 310 ~um Weight per un;t area : 205 g/m2.
The greige fabric is coated with PVC plastisol containing 8X by we;ght of titanium dioxide as a white pigment. After careful drying, the coating contains 41Z
by weight of plasticizer. The weight per unit area is 750 to 800 g/m2.
B) A top layer composed of polymethyl methacrylate and plasticized PVC tplasticizer content 41% by weight) is applied to both sides of this substrate in a ratio of 60:40 parts by weight. The weight per unit area of the top layer is about 8 g/m2.
Preparation of the composite materials according to the invention Example 1 A fluorine-containing copolymer of the following com-posit;on: 30 X by we;ght of copolymerized vinylidene fluoride un;ts, 15X by we;ght of copolymerized hexafluoropropylene units and 55X by weight of copolymerized tetrafluoroethylene units (melting point 154C) is applied from a 50X strength by weight aqueous dispersion by means of the air spraying process to one side of the abovementioned PVC substrate which has been provided with the top layer.
A continuous sealing film is then formed by heat-ing at 180C for 15 minutes. The sealing layer applied amounts to 17 g/m2.
Example 2 A fluorine-containing copolymer having the 123~3828 following composition: 40% by weight of copolymerized vinylidene fluoride units, 20X by weight of copolymerized hexafluoropropylene units and 40% by weight of copoly-merized tetrafluoroethylene un;ts ;s appl;ed from an aqueous d;spers;on (50X by weight) by the procedure of Example 1 to the abovementioned PVC substrate which has been provided with a top layer, and the coating is then heated and kept at a temperature of 160C for 15 minutes. Amount appl;ed: 15 g/m2.
Example 3 The fluorine-containing copolymer described in Example 2 is applied by the same process to the same substrate, but in this case from a 5Z strength by weight solution in methyl ethyl ketone, and is then first dried for 15 minutes at 70C and then for 15 minutes at 170C
and is baked. Amount applied: 14 g/m2.
Example 4 A top layer mixture is applied to one s;de of the PVC-coated polyester fabric A) by means of a doctor kn;fe. Th;s m;xture ;s obta;ned by add;ng 15 parts by we;ght of the acryl;c res;n mixture descr;bed under B), composed of polymethyl methacrylate and plast;cized PVC
in a ratio of 60:40 parts by weight, to 85 parts by weight (as a 20X strength by we;ght solution in methyl ethyl ketone) of the fluorine-containing copolymer des-cribed ;n Example Z.
The lam;nate thus obtained is first dried for 10 m;nutes at 70C and is then baked for a further 10 minutes at 160C. The amount applied is 18 g/m2.
Example 5 A top layer mixture is applied to one side of the PVC-coated polyester fabric A) by means of a doctor kn;fe. Th;s m;xture ;s obta;ned by add;ng 90 parts by we;ght of the acryl;c resin m;xture descr;bed under B), composed of polymethyl methacrylate and plasticized PVC
in a ratio of 60:4û parts by weight, to 10 parts by we;ght (as a 20X strength by we;ght solut;on in methyl ethyl ketone~ of the fluorine-containing copolymer des-cribed ;n Example 2. The top layer thus obtained is ~238828 dried for 10 minutes at 100C. The amount applied is 5 g/m2.
A sealing layer composed solely of the fluorine-conta;ning copolymer described in Example 2, but in this case as 3 20X strength by weight solution in methyl ethyl ketone, is also applied by means of the doctor knife to this layer. The laminate ;s first dried for 10 min-utes at 70C and is then baked for 10 minutes at 160C.
The amount of seal;ng layer appiied is 15 g/m2.
Compar;son tests PVC substrates, prepared in accordance with ;nstruct;ons A) and composed either only of the acrylic resin mixture b1) (60:40 polymethyl methacrylate and plastic;zed PVC) or of the mixture, indicated in Example 4, of an acrylic resin mixture of this type with the fluo-rine-containing copolymer b1) plus b2), are coated as described in the instructions under B) and in Example 4.
For comparison, the same PVC substrate is coated solely with the fluorine-containing copolymer of Example 2 as a 20% strength by we;ght solution ;n methyl ethyl ketone.
The seal;ng layer can be removed in one strip from this comparison sample in the fingernail test, whereas, with the compos;te mater;als according to the invention, although damage can be caused to the sealing layer or the top layer, the;r removal cannot be achieved even by repeated scratching.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A composite material which comprises a) a substrate layer composed essentially of plasticized PVC, and b) a top layer, applied to one or both sides of this substrate layer and composed of:
b1) 5 to 100 % by weight of a mixture of acrylic resins composed of 5 to 60 % by weight of plasticized PVC
or an internally plasticized copolymer of vinyl chloride and - to bring the total up to 100 % by weight, - an acrylic resin, and b2) 0 to 95 % by weight of a fluorine-containing copolymer containing 50 to 20 % by weight of co-polymerized units of vinylidene fluoride, 10 to 30 % by weight of copolymerized units of hexafluoro-propylene and copolymerized units of tetrafluoro-ethylene, the proportion of the latter being at least 30 % by weight in the copolymer, and co-polymerized units of another fluoroolefin or fluoro-alky vinyl ether in an amount of 0 to 5 % by weight, subject to the proviso that, if the content of the fluorine-containing copolymer b2) in the top layer is 0 to 15 % by weight, there is also provided, on the latter, c) a sealing layer which is solely composed of the fluorine-containing copolymer defined under b2).

2. A composite material as claimed in claim 1, wherein the substrate layer a) is a woven or knitted fabric or non-woven composed of textile materials which has been coated with plasticized PVC:

3. A composite material as claimed in claim 1, wherein the substrate layer a) is a polyester fabric which has been coated with plasticized PVC.

4. A composite material as claimed in claim 1, wherein the acrylic resin of the top layer is polymethyl meth-acrylate.

5. A composite material as claimed in claim 1, wherein the acrylic resin of the top layer is a mixture of polymethyl methacrylate and polybutyl acrylate.

6. A composite material as claimed in claim 1, wherein the acrylic resin of the top layer is mixed with an internally plasticized copolymer of vinyl chloride containing at least one monomer from the group comprising vinyl acetate, acrylic acid esters, methacrylic acid esters, maleic acid esters of fumaric acid esters.

7. A composite material as claimed in claim 1, wherein the top layer is composed of 5 to 30 % by weight of the acrylic resin mixture b1) and 70 to 95 % by weight of the fluorine-containing copolymer b2).

8. A composite material as claimed in claim 1, wherein the fluorine-containing copolymer of the sealing layer con-tains 45 to 30 % by weight of copolymerized units of vinylidene fluoride, 15 to 25 % by weight of copolymerized units of hexafluoropropylene and at least 30 % by weight of copolymerized units of tetrafluoroethylene as well as copolymerized units of another fluoroolefin or fluoro-alkyl vinyl ether in an amount of 0 to 5 % by weight.

9. The composite material as claimed in claim 1 in the form of a roofing web.

10. The composite material as claimed in claim 1 in the form of an air-inflated structure.