US3615106A

US3615106A - Manufacture of hard covered books

Info

Publication number: US3615106A
Application number: US813770A
Authority: US
Inventors: Thomas P Flanagan; Paul P Puletti
Original assignee: National Starch and Chemical Corp
Current assignee: Ingredion Inc
Priority date: 1969-04-04
Filing date: 1969-04-04
Publication date: 1971-10-26
Anticipated expiration: 1988-10-26
Also published as: NL7003134A; GB1256814A; DE2015979B2; NL140542B; DE2015979A1; FR2039076A5

Abstract

A METHOD FOR BINDING HARD COVERED OR EDITION BOUND BOOKS WHEREIN THE HOT MELT ADHESIVE COMPOSITION WHICH IS UTILIZED COMPRISES A BLEND OF (A) A COPOLYMER OF ETHYLENE WITH EITHER VINYL ACETATE OR AN ALKYL ACRYLATE COMONOMER, (B) A TACKIFYING RESIN, (C) POLYETHYLENE, AND (D) A DILUENT. THE DESCRIBED COMPOSITIONS EXHIBIT A HIGH DEGREE OF PERMANENT SET WHICH IS PARTICULARLY USEFUL IN BINDING ROUNDED, HARD COVERED BOOKS.

Description

United States Patent Ofiice 3,6l5,lil6

Patented Oct. 26, 1971 3,615,106 MANUFACTURE OF HARD COVERED BOOKS Thomas P. Flanagan, Green Brook, and Paul P. Puletti, Glen Gardiner, N.J., assignors to National Starch and Chemical Corporation, New York, N.Y. No Drawing. Filed Apr. 4, 1969, Ser. No. 813,770 Int. Cl. (108i 43/08 U.S. Cl. 281-21 Claims ABSTRACT OF THE DISCLOSURE A method for binding hard covered or edition bound books wherein the hot melt adhesive composition which is utilized comprises a blend of (a) a copolymer of ethylene with either vinyl acetate or an alkyl acrylate comonomer, (b) a tackifying resin. (c) polyethylene, and (d) a diluent. The described compositions exhibit a high degree of permanent set which is particularly useful in binding rounded, hard covered books.

The manufacture of hard covered books involves unique features of construction and operation which are not required in other methods of bookbinding. Thus, in this operation, the pages are printed either in long, continuous sheets or in individual sheets which are cut, folded and properly arranged to form a series of stacks, referred to as signatures which are, in essence, a plurality of sheets. These signatures are collected and then enclosed by means of end papers which are typically adhered to the outer leaves of the first and last signatures. Thereafter, the signatures are transferred to sewing machines where they are sewn individually and to one another. Adhesives are then applied to the sewn edges of the signatures in a gluing off operation which provides greater rigidity to the book body so as to enable it to withstand subsequent trimming and handling operations. The bound signatures are then rounded, i.e. deformed such that a curvature is impressed on the back edge of the book, backed and then lined-up in a procedure which involves the application of hot glue to the rounded surface and the attachment of a strip of fabric, usually crash, and backing paper thereto. The books are then ready for the final casingin operation wherein the hard cover is attached to the bound book.

Although the use of the hot metal adhesives has met with commercial success in the binding of paper-backed books, i.e. soft covered books, wherein they have served to increase the rate of output, to eliminate the stitching and stapling step, and to provide more permanent bindings, serious limitations have been encountered when attempts have been made to use hot melts in the binding of hard covered books. These limitations have been especially noted in the critical rounding step of the binding operation, i.e. the step wherein a curvature is impressed on the back edges of the book body and where the rear portions of the outermost signatures are bent into a flange-like projection along each side of the back edge so that the cover boards may be closely fitted to the assembled body of leaves while permitting the hinge portions thereof to have ample freedom of motion without exhibiting any tendency to become torn or pulled out of place.

Currently available hot melt adhesives either: (1) provide adhesive films which are too rigid to be impressed into a rounded configuration or which split in the attempt, thereby losing their film continuity and enabling the pages to separate from the bound signatures; or, (2) they provide adhesive films which, although forming the desired rounded configuration, exhibit an excessive plastic flow. In the latter instance, the excellent elastic memory exhibited by these films causes them to abandon the required rounded configuration and to revert to the configuration which they assumed prior to the rounding operation. Therefore, since the critical rounded configuration is not provided in either instance, it becomes obvious that the currently available hot melt adhesives are not readily applicable for use in the binding of rounded, hard covered books but, instead, must be limited for use in the preparation of the undesirable square-backed, hard covered books.

It is the prime object of this invention to provide an adhesive composition which exhibits excellent adhesive strength and a high degree of permanent set, thereby enabling it to be effectively utilized in the binding of hard covered books. 4

It is still a further object that the adhesive be deposited by means of applicator equipment conventional in the bookbinding industry. Still another object is to provide an adhesive which may be handled in bulk form for use in the premelting equipment presently available in the industry; or, which may be pelletized, diced, or granulated for convenient premelting in an applicator of the extruder type; or, which may be utilized in rope or cord form for applicators designed to handle adhesives in the latter physical forms. Various other objects and advantages of this invention will become apparent to the practitioner from the following detailed description thereof.

We have now discovered that by utilizing hot melt adhesive compositions, as hereinafter described, in the binding of hard covered books, it is possible to overcome substantially all of the difficulties previously encountered in the binding of this type of book. Thus, the hot melt adhesives used in the process of this invention exhibit the rubbery characteristics and adhesive strength which are essential to bind the individual book pages. Furthermore, these hot melt adhesive products display good heat stability, rapid setting speed, and excellent adhesion to a variety of cellulosic and non-cellulosic materials such, for example, as all types of paper stocks, waxed-glassine sheets, metallic foils, polyester sheets, etc. Of particular importance, however, is the fact that these hot melts exhibit a high degree of permanent set. Thus, their adhesive films which serve to bind the books are capable of being deformed to correspond to the desired rounded configuration of the back of the book and, due to poor elastic memory, of permanently retaining this rounded configuration. It is the combination of these essential properties in the hot melts of this invention that now permits the manufacture of quality, permanently bound, rounded, hard covered books at high production speeds.

The hot melt adhesive compositions utilized in the process of this invention comprise a blend of: (a) from about 20 to 40%, by weight, of a copolymer of ethylene with one or more comonomers selected from the group consisting of vinyl acetate and the alkyl esters of acrylic acid, said copolymer representing the base polymer component of the hot melt system; (b) from about 15 to 45%, by weight, of at least one tackifying resin which serves to extend the adhesive properties. of the hot melt system; (c) from about 5 to 15%, by weight, of polyethylene having certain specified characteristics which serves to lower the elastic memory of the hot melt system; and, (d) from about 10 .to 40%, by weight, of a diluent which serves to reduce the melt viscosity or cohesive characteristics of the hot melt adhesive system without decreasing its adhesive binding characteristics.

In more detail, the base polymer component of the adhesive systems is a copolymer of ethylene obtained by the polymerization of ethylene with either vinyl acetate or one or more alkyl esters of acrylic acid wherein said alkyl group contains from 1 to about 4 carbon atoms. The ethylene copolymers useful in the present hot melt adhesive compositions should contain from about 70 to 85%, by weight, of ethylene.

The ethylene:vinyl acetate copolymers may be prepared by means of procedures well known to those skilled in the art, such, for example, as the process described in U.S. Pat. 3,282,881. The ethylenezvinyl acetate copolymers useful in the present adhesive compositions should have an inherent viscosity, as determined at 86 F. in a 0.25% solution of the copolymer in toluene, of about 0.75 to 1.05 and a Melt Index, as determined by American Society for Testing Materials (ASTM) method D 1238, within the range of from about 1.5 to 20.0.

The ethylenezalkyl acrylate copolymers are also prepared by means of polymerization procedures well known in the art. For example such copolymers can be prepared using 'free radical initiated polymerization techniques whereby a mixture of ethylene and an alkyl acrylate monomer is heated in the presence of a catalyst such as benzoyl peroxide, or an azo compound such as azobisisobutyronitrile, and the like. The procedure may be carried out either batch-wise or continuously under pressures ranging from about 5,000 to about 50,000 pounds per square inch and at temperatures ranging from about 200 to about 580 F.

As noted hereinabove, suitable alkyl acrylate monomers which may be copolymerized with ethylene to form a copolymer component for use in the hot melt adhesives of the invention are those containing from 1 to about 4 carbon atoms in their respective alkyl radicals. Examples of such comonomers are methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, and isobutyl acrylate. The ethylene:alkyl acrylate copolymers useful in these adhesive compositions should have an inherent viscosity, as determined at "86 F. in a 0.25% solution of the copolymer in toluene, of about 0.6 to 1.1 and a Melt Index within the range of from about 1.0 to 20.0.

It is to be noted that, if desired, one or more ethylenically unsaturated carboxylic acids such, for example, as acrylic, methacrylic, fumaric, citraconic or itaconic acid, and the like, can be incorporated into the copolymers described above in a concentration such that the acid number of the resultant polymer is not greater than about 8. Their presence in such copolymers does not appreciably change the behavioral characteristics of the modified copolymers when utilized in the adhesive blends of the subject process.

The tackifying resins which are present in the hot melt systems of the subject process serve to extend the adhesive properties of these described hot melt systems. As contemplated in this invention, the term tackifying resin includes: 1) natural and modified rosins such, for example, as gum rosin, wood rosin, tall-oil rosin, distilled rosin, hydrogenated rosin, dimerized rosin, and polymerized rosin; (2) glycerol and pentaerythritol esters of natural and modified rosins such, for example, as the glycerol ester of pale wood rosin, the glycerol ester of hydrogenated rosin, the glycerol ester of polymerized rosin, the pentaerythritol ester of hydrogenated rosin, and the phenolic-modified pentaerythritol ester of rosin; (3) polyterpene resins having a softening point, as determined by ASTM method B 28-58 T, of from about 176 to 302 F.; the latter polyterpene resins generally resulting from the polymerization of terpene hydrocarbons, such as the bicyclic mono-terpene known as pinene, in the presence of Friedel-Crafts catalysts at moderately low temperatures; (4) chlorinated biphenyl or terphenyl resins; (5) phenolic-modified terpene resins such, for example, as the resin product resulting from the condensation in an acidic medium of a bicyclic terpene and phenol; and (6) aliphatic petroleum hydrocarbon resins having a Ball and Ring softening point of from about 176 to 257 R; an acid number of from about 0 to 2; a saponification value of less than about 1; and, an iodine value of from about 75-100. The latter class of tackifying resins are ordinarily obtained during the polymerization of olefins and diolefins, and they may comprise, for example, polymers based on the residual byproduct monomers produced during the manufacture of isoprene. Examples of commercially available resins of this type are Wing-Tack sold by the Goodyear Tire and Rubber Co. and the Sta-Tao and Betaprene H resins sold by Reichhold Chemicals, Inc.

The polyethylene component which functions as aforesaid to reduce the elastic memory of the adhesive composition must have a density ranging from about 0.91 to 0.96, as determined by ASTM method D 1505, and a Melt Index ranging from about 1 to 200, as determined by ASTM method D 1238. It is to be noted that a high degree of permanent set is a particularly desirable property of any hot melt composition which is to be used in the binding of rounded, hard covered books and it is only by utilizing polyethylene having these defined characteristics that we have been able to provide hot melts displaying this useful property. Thus, the use of polyethylenes which do not fall within the above specified density and Melt Index ranges does not enhance the degree of permanent set of the hot melt compositions wherein they are present, and such formulations are of little or no value in the preparation of rounded, hard covered books. The so-called polyethylene greases which, as noted herein below, are useful as diluents in the present adhesive compositions wherein they serve to reduce their viscosity, are to be particularly distinguished from the polyethylene described hereinabove inasmuch as the presence of these polyethylene greases has no appreciable effect on the elastic memory of the adhesives.

The distinction between polyethylene having this density from about 0.91 to 0.96 and a Melt Index from about 1 to 200 and the polyethylene greases are based upon their respective molecular weights. Thus, the polyethylene resins useful in reducing the degree of elastic memory in the adhesives of the invention should have a molecular weight of at least about 10,000. On the other hand, the polyethylene greases have molecular weights which are substantially below those of the polyethylenes whose presence is required in our adhesive compositions. However, since it is extremely diflicult to determine the molecular weight of the higher molecular weight polyethylenes, various other physical constants are ordinarily used in describing these polymers. For example, the higher molecular weight polyethylenes required in our adhesives are usually characterized in terms of their Melt Index which can be conveniently determined by means of ASTM method D 1238. However, the latter test procedure is inapplicable for use with the lower molecular weight polyethylene greases since the greases are far too fluid to provide meaningful results with this test technique. For this reason, these fluid low molecular wewight greases are usually described in terms of their hardness values, softening points, molten viscosities, or actual molecular weights.

As previously stated, a diluent or mixture thereof is employed in our adhesive systems in order to reduce the melt viscosity or cohesive characteristics of the hot melt adhesive compositions without appreciably decreasing its adhesive binding characteristics. Among the applicable diluents are included: (1) low molecular weight, liquid polybutylene in the range of from about 600 to 3000; (2) petroleum waxes such as parafi in wax having a melting point of from about l30l65 F. and microcrystalline wax having a melting point of from about l40200 F.; the latter melting points being determined by ASTM method D 127-60; (3) polyethylene greases or waxes having a softening point of from about 176-230 F. and a hardness value, as determined by ASTM method D 1321, of from about 2-100; (4) hydrogenated animal, fish and vegetable fats and oils such as hydrogenated tallow, lard, soya oil, cottonseed oil, castor oil, menhaden oil and cod liver oil, etc.; mineral oil; and, (6) synthetic waxes made by polymerizing carbon monoxide and hydrogen, such as Fischer-Tropsch wax.

In addition to the above described components, the hot melt adhesive compositions may contain various optional additives in order to modify certain properties of the compositions for particular end-use applications. Thus, optional additives which may be incorporated into the hot melt compositions used in this invention include: antioxidants or stabilizers, such as high molecular weight hindered phenols including, for example, 1,3,5-trimethyl- 2,4,6-tris (3,5 di-tert-butyl-4-hydroxybenzyl) benzene; 4,4'-thiobis (6 tert-butyl-o-cresol); and, di-n-octadecyl 3,S-di-tert-butyl-4-hydroxy-benzylphosphonate; pigments such as titanium dioxide; and, fillers such as talc, clay, and the like.

The procedure for preparing these hot melt adhesive compositions involves the melting of the tackifying resin and diluent in a steam or oil jacketed mixing kettle, preferably in a jacketed heavy duty mixer of the Baker Perkins or Day type, which is equipped with means for mechanical agitation. The melting of the latter components is carried out at temperatures of from about 250 to 350 F. The precise temperatures used will depend, of course, on the melting points of the particular tackifying resin and diluent which are being employed. When the two components are melted, the polyethylene and the ethylene copolymer are added with sutficient agitation to avoid lumping. Stabilizers and other optional ingredients may also be added at this point. Mixing and heating are continued until a smooth homogeneous mass is obtained whereupon the resulting hot melt adhesive is then withdrawn from the kettle in molten form. The adhesive may be utilized immediately or, alternatively, it may be extruded into rope form or converted into pellets, rods, slugs, cylinders, or billets, depending on the equipment which will be subsequently used to apply the adhesive during the binding operation; or it may be placed in cooling pans and held in bulk form for later use; or it may be granulated or diced.

The resulting hot melt adhesive compositions, as described hereinabove, are typically applied at temperatures of from about 300 to 400 F., and a corresponding melt viscosity of from about 5000 to 40,000 centipoises. Coatings having a wet film thickness of from about 5 to 30 mils are ordinarily utilized in preparing the rounded, hard covered books by means of the process of this invention.

As previously noted, the basic technique for binding rounded, hard covered books, as contemplated by the novel process of this invention, comprises the steps of: (1) printing, cutting, folding and enclosing the collected signatures by means of end papers; (2) sewing the signatures individually and to one another; (3) applying the hot melt adhesive composition to the sewn edges of the signatures in a gluing off operation; (4) allowing the adhesive to solidify at ambient temperatures or by means of forced cooling; (5) rounding the bound signatures, i.e. mechanically deforming the backbone, and concurrently the front face, to the shape commonly employed in the manufacture of hard covered books; (6) lining-up the bound sheets, i.e. applying crash or like fabric to a freshly applied hot melt adhesive coating which may or may not be identical to the previously utilized hot melt composition; (7) enclosing the bound sheets in endpapers or interlining, if such end-papers have not previously been bound into the book body; and (8) casingin the bound book within hard covers. As an alternative step, the crash or like material may be applied to the partially solidified hot melt coating at a point which is intermediate, timewise, between steps 3 and 4, as contrasted with its more conventional application at step 6; the use of the latter sequence being dependent upon the particular bookbinding equipment that is being utilized. In either instance, this novel procedure results in the preparation of rugged, durable, hard covered books which are substantially free from such difliculties as loss of their rounded configuration and separation of their bound pages.

Although great emphasis has been placed, in this disclosure on the use of the described hot melt compositions in the binding of rounded, hard covered books utilizing a gluing oif procedure, it should be noted that these adhesives may also be effectively utilized in the perfect binding, i.e. wherein sewing of the signatures is not required and the signature folds are cut so as to expose a fully squared backbone, of hard covered books and soft covered books such as pocket books, magazines, catalogs, brochures, etc. Perfect bound, rounded, hard covered books can also be manufactured.

The following examples will further illustrate the embodiment of this invention. In these examples all parts given are by Weight unless otherwise noted.

EXAMPLE I This example illustrates the preparation of a hot melt adhesive composition typical of the products used in the process of this invention as well as the improved properties thereof which enable it to be effectively utilized in the binding of hard covered books.

A heavy duty mixer which had been heated to 300 F. and which was equipped with a stirring paddle was charged with 35 parts of a pentaerythritol ester of rosin and 30 parts of microcrystalline wax having a melting point of 180 F. When the above components were melted, stirring was initiated and 7 parts of polyethylene having a density of 0.95 and a Melt Index of 11 were added, followed by the addition of 28 parts of an ethylenezvinyl acetate copolymer having a vinyl acetate content of 25%, by weight, and Melt Index of 2.0. Heating and stirring were continued until a clear, homogeneous mass was obtained.

The resulting homogeneous hot melt composition had a melt viscosity of 21,500 centipoises (cps) at 350 F., as determined by a Brookfield viscoimeter using a #6 spindle at 20 rpm.

In order to demonstrate the applicability of the above prepared hot melt to book binding operations, it was subjected to the following test procedures:

Low Temperature Flexibility The molten hot melt was cast, by means of a heated Bird applicator, onto a polytetrafiuoroethylene-coated steel plate yielding a film having a dry film thickness of 20 mils. After cooling, the film specimen was stripped from the plate and cut into /2 x 2 inch test specimens. A representative specimen was then placed in a temperature controlled, carbon dioxide cabinet for a period of 10 minutes whereupon it was immediately flexed at a 30 angle. Where the specimen did not crack as a result of this procedure, a second identical specimen was placed in the cabinet at a lower temperature and the flexing procedure repeated. The temperature at which the specimen eventually cracked was thus viewed as its low temperature flexibility value. Thus, as the latter value is decreased, there is a corresponding increase in the flexibility and stability which can be expected upon exposing these films and the books bound therewith to low temperature conditions.

Tensile Strength This property was determined on films cast from the hot melts according to Test Method A of ASTM procedure D 882-56 T utilizing an lnstron Tensile Tester; the latter 7 films having been prepared according to the method set forth in the above described Low Temperature Flexibility test.

The films derived from the hot melt adhesive composition of this example exhibited a Low Temperature Flexibility value of 10 to F. and a tensile strength of 1,055 p.s.l.

Upon coating the above prepared molten hot melt composition onto the sewn edges of compressed signatures as part of a bookbinding process, an adhesive film was quickly formed, which upon setting or cooling, produced an excellent spine binding.

The above described properties of this hot melt composition thus indicate its usefulness in the binding of books.

EXAMPLE II In order to demonstrate the high degree of permanent set exhibited by the hot melt compositions described herein and, thereby, their applicability for use in bookbinding operations wherein rounding is a critical feature, each of the compositions, as described hereinbelow, was subjected to a test procedure whereby it was cast, by means of a heated Bird applicator, onto a polytetrafiuoroethylenecoated steel plate yielding a film having a dry thickness of mils. After cooling, the film was stripped from the plate and cut into /2 by 2 inch test specimens. Each specimen was then elongated to approximately 500% of its original length and, after the stress was relaxed, allowed to reach equilibrium for a period of 24 hours. The specimen was then measured in order to determine the extent to which it had reverted to its original length.

The binding of rounded, hard covered books requires the use of hot melt adhesives exhibiting a low elastic memory and a low Percent Recovery value, i.e. a value of about 25 to 55%, is preferred for such use. i

The procedure set forth in Example I, hereinabove, was utilized in preparing each of the following hot melt compositions. The melt viscosity values at 350 F., as determined by a Brookfield viscosimeter using a #6 spindle at 20 rpm, and the Low Temperature Flexibility and tensile strength, as determined by procedures described in Example I, hereinabove, are provided in order to characterize each of the thus prepared compositions with respect to their suitability for use as adhesives in a bookbinding process.

Composition A Parts Ethylenezethyl acrylate copolymer containing by weight, of ethyl acrylate and having a Melt Index of 2.5 Pentaerythritol Ester of Hydrogenated Wood Rosin (Ball and Ring S.P. 221 F.) 35 Microcrystalline Wax, melting point 180 F. 30

Composition B Ethylene:ethyl acrylate copolymer containing 30%, by weight, of ethyl acrylate and having a Melt Index of 2.5 28 Pentaerythritol ester of hydrogenated wood rosin (Ball and Ring S.P. 221 F.) 35 Microcrystalline Wax, melting point 180 F 30 Polyethylene having a density of 0.938 and a Melt Index of 8.0 7

Composition C Ethylenezvinyl acetate copolymer containing 18%, by weight, of ethyl acrylate and having a Melt Index of 2.5 28 Pentaerythritol ester of hydrogenated wood rosin (Ball and Ring S.P. 221 F.) 35 Microcrystalline wax, melting point 180 F. 30 Polyethylene having a density of 0.938 and a Melt Index of 8.0 7

The following table summarizes the test results, including Percent Recovery values, obtained with films of the above described hot melt compositions.

TABLE I Compositions A B C Melt Viscosity (cps) 350 F 11, 000 12,000 17, 500 Low Temperature Flexibility, F 0 to 5 0 to 5 -5 to 0 Tensile Strength (p.s.i.) 665 655 950 Percent Recovery, percent G1 55 30 EXAMPLE III This example illustrates the preparation of a number of hot melt adhesive compositions useful in the process of this invention; the latter compositions containing a variety of different components in varying proportions.

The procedure set forth in Example I, hereinabove, was utilized in preparing each of the below described hot melt compositions. The melt viscosity values, Low Temperature Flexibility, tensile strength, and Percent Recovery values, determined as described hereinabove, are provided in order to characterize each of the thus prepared compositions.

Composition A Parts Ethylenezvinyl acetate copolymer containing 25%,

by weight, of vinyl acetate and having a Melt Index of 2.0 28 Microcrystalline wax, melting point 180 F. 30 Alpha-pinene polymer (Ball and Ring S.P. 239 F.) 35 Polyethylene having a density of 0.938 and 2. Melt Index of 8.0 7 1,3,5 trimethyl-2,4,6-tris (3,5-di-tert-butyl-4hydroxyi benzyl) benzene 0.1

This composition had the following properties:

Melt Viscosity-18,000 cps.

Low Temperature Flexibility-0 to 5 F. Tensile Strength935 p.s.i.

Percent Recovery25 Composition B The formulation of this composition was the same as that of Composition A, hereinabove, except that the poly terpene tackifying resin was replaced by an aliphatic petroleum hydrocarbon resin having a softening point of 212 F. This composition had the following properties:

Melt Viscosity-l0,875 cps.

Low Temperature Flexibility30 to 35 F. Tensile Strength-610 p.s.i.

Percent Recovery28%.

Composition C Parts Copolymer of Composition A 28 Microcrystalline wax, melting point 180 F. 5 Parafiin wax, melting point F 25 Pentaerythritol ester of rosin 35 Polyethylene having a density of 0.95 and a Melt Index This composition had the' following properties:

Melt Viscosity17,250 cps. Low Temperature Flexibility-25 to 30 F. Tensile Strength-1,200 p.s.i. Percent Recovery-35%.

Composition D Parts Ethylene:vinyl acetate copolymer containing 25%, by

weight, of vinyl acetate and having a Melt Index of 6.0 28 Microcrystalline wax, melting point 180 F 30 Aliphatic petroleum hydrocarbon resin having a softening point of 212 F 35 Polyethylene having a density of 0.92 and a Melt Index of 2.0 7

This composition had the following properties:

Melt Viscosity-16,000 cps. Low Temperature Flexibility25 to 30 F. Tensile Strength850 p.s.i. Percent Recovery33%.

Composition E Parts Copolymer of Composition A 30 Tackifying resin of Composition D 35 Microcrystalline wax, melting point 180 F 30 Polyethylene having a density of 0.938 and a Melt Index of 8.0

This composition had the following properties:

Melt Viscosityl2,750 cps.

Low Temperature Flexibility-25 to 30 F. Tensile Strength900 p.s.i.

Percent Recovery 28%.

Composition F The formulation of this composition was the same as that of Composition A, hereinabove, except that the polyethylene used in the latter example was replaced by a polyethylene having a density of 0.95 and a Melt Index of 11.0. This composition had the following properties:

Melt Viscosity-24,700 cps.

Low Temperature Flexibility35 to 40 F. Tensile Strength870 p.s.i.

Percent Recovery25 Composition G The formulation of this composition was the same as that of Composition F, hereinabove, except that the ethylene copolymer used in the latter formulation was replaced by an ethylene-vinyl acetate copolymer containing 28%, by weight, of vinyl acetate and having a Melt Index of 6.0. This composition had the following properties:

Melt Viscosity-12,750 cps.

Low Temperature Flexibility-30 to 35 F. Tensile Strength690 p.s.i.

Percent Recovery-25 Upon coating each of the above described hot melt compositions onto the sewn edges of compressed signatures, an adhesive film was quickly formed which, upon setting, produced an excellent spine binding. The signatures were then deformed to produce a rounded back and the above described hot melt compositions were again applied to the back prior to the application of crash. Excellent results were achieved in all cases.

EXAMPLE IV This example illustrates the critical change in the properties displayed in a typical adhesive composition of this invention when a polyethylene grease is substituted for the required polyethylene having a density of from 0.91 to 0.96 and a Melt Index of from 1 to 200. Formulations described in this example Were prepared by means of the procedure set forth in Example I, hereinabove.

Composition A Parts Ethylenezvinyl acetate copolymer containing 28%, by weight, of vinyl acetate and having a Melt Index of 5.0 28 Microcrystalline Wax, melting point 180 F. 30 Pentaerythritol ester of rosin 35 Polyethylene having a density of 0.938 and a Melt Index of 8.0 10

Composition B This formulation was identical to Composition A, hereinabove except that the higher molecular weight polyethylene utilized therein was replaced with a polyethylene grease having a molecular weight of only 2000 and a molten viscosity of 200 centipoises at 140 C.

The resulting formulations displayed the following properties:

Composition Melt Viscosity (cps) 350 F 15,000 i, 250 Low Temperature Flexibility, F 0 to 5 5 to 10 Tensile Strength (p.s.i.) 1,100 1,000 Percent Recovery, percent 45 60 Thus, it is clearly evident that use of a polyethylene grease as the polyethylene component of the adhesive compositions of this invention results in the preparation of adhesives which are characterized by an exceedingly low melt viscosity value and whose Percent Recovery value, on the other hand, has been increased to an undesirably high level.

EXAMPLE V This example illustrates the preparation of two additional varieties of hot melt adhesive compositions suitable for use in the process of this invention. These compositions were prepared by the procedure set forth in Example 'I, hereinabove.

Composition A Upon coating the above described hot melt compositions onto the sewn edges of compressed signatures, adhesive films were formed which, upon setting, produced excellent spine bindings.

Summarizing, it is thus seen that this invention provides novel hot melt adhesives for an improved method for the binding of books. Variations may be made in proportions, procedures and materials without departing from the scope of this invention which is limited only by the following claims.

We claim:

1. A hot melt adhesive composition comprising a blend of: (1) from about 20 to 40%, by weight, of a copolymer of ethylene with at least one comonomer selected from the group consisting of vinyl acetate and the alkyl esters of acrylic acid, said copolymer containing from about 70 to by weight, of ethylene; (2) from about 1 1 15 to 45%, by weight, of at least one tackifying resin selected from the group consisting of: (a) natural and modified rosins, (b) glycerol and pentaerythritol esters of natural and modified rosins, (c) polyterpene resins having an ASTM softening point of from about 176 to 302 F., (d) chlorinated biphenyl or terphenyl resins, (e) phenolicmodified terpene resins, and (f) aliphatic petroleum hydrocarbon resins having a Ball and Ring softeningpoint of from about 176 to 257 R, an acid number of from about to 2, a saponification value of less than about 1, and an iodine value of from about 75 to 100; (3) from about to by weight, of a polyethylene having a density ranging from about 0.91 to 0.96 and a Melt Index ranging from about 1 to 200; and, (4) from about 10 to 40%, by weight, of a diluent selected from the group consisting of: (a) liquid polybutylene having a molecular weight in the range of from about 600 to 3000", (b) petroleum Waxes having a melting point of from about 130 to 200 F (c) polyethylene greases and waxes having a softening point of from about 176 to 230 F. and an ASTM hardness value of, from about 2 to 100, (d) hydrogenated animal, fish and vegetable fats and oils, (e) mineral oil, and (f) Fischer-Tropsch Wax.

2. A hot melt adhesive composition comprising a blend of: (1) about 28 parts, by weight, of an ethylenezvinyl acetate (72:28) copolymer; (2) about 35 parts, by weight, of a pentaerythritol ester of rosin; (3) about 10 parts, by Weight, of polyethylene having a density of 0.938 and a Melt Index of 8.0; and, (4) about 30 parts, by weight, of microcrystalline Wax having a melting point of 180 F.

3. A hard covered book containing a plurality of sheets which are bound toone another at the backbone of said book by means of the dried, consolidated residue of a hot melt adhesive composition comprising a blend of: (1) from about to 40%, by weight, of a copolymer of ethylene with at least one comonomer selected from the group consisting of vinyl acetate and the alkyl esters of acrylic acid, said copolymer containing from about 70 to 85%, by weight, of ethylene; (2) from about 15 to 45%, by weight, of at least one tackifying resin selected from the group consisting of: (a) natural and modified rosins, (b) glycerol and pentaerythritol esters of natural and modified rosins, (c) polyterpene resins having an ASTM softening point of from about 176 to 302 F., (d) chlorinated biphenyl or terphenyl resins, (e) phenolic-modified terpene resins, and (f) aliphatic petroleum hydrocarbon resins having a Ball and Ring softening point of from about 176 to 257 R, an acid number offrom about 0 to 2, a-saponification value of less than about 1, and an iodine value of from about to '100; (3) from about 5 to 15 by Weight, of a polyethylene having a density ranging from about 0.91 to 0.96 and a Melt index ranging from about 1 to 200; and, (4) from about 10 to 40%, by weight, of a diluent selected from the group consisting of: (a) liquid poly-butylene having a molecular weight in the range of from about 600 to 3000, (b) petroleum Waxes having a melting point of from about to 200 F., (c) polyethylene greases and Waxes having a softening point of from about 176 to 230 F. and an ASTM hardness value of from about 2 to 100, (d) hydrogenated animal, fish and vegetable oils and fats and oils, (e) mineral oil, and (f) Fischer- Tropsch wax.

4. The hard covered book of claim 3, wherein said backbone of said book has a rounded configuration.

5. A hard covered book containing a plurality of sheets which are bound to one another at the backbone of said book by means of the dried, consolidated residue of a hot melt adhesive composition comprising a blend of: (1) about 28 parts, by Weight, of an ethylenezvinyl acetate (72:28) copolymer; (2) about 35 parts, by weight, of a pentaer ythritol ester of rosin; (3) about 10 parts by Weight, of polyethylene having a density of 0.938 and a Melt Index of 8.0; and, (4) about 30 parts by Weight, of microcrystalline wax having a melting point of 180 F.

References Cited UNITED STATES PATENTS 2,772,247 11/1956 Schroeder 260897 X 3,084,128 4/ 1963 Stillwagon 2604 3,201,498 8/1965 Br'unson et al. 260897 3,223,436 12/1965 Becker 28121 3,282,881 11/1966 Flanagan 26033.8 3,366,589 l/ 1968 Hammer et a1. 260897 X 3,448,178 6/1969'. Flanagan 260897 3,468,978 9/1969 Battersby 260897 3,485,783 12/1969 Kebe 260897 X DONALD E. CZAJA, Primary Examiner D. J. BARRACK, Assistant Examiner US. Cl. X.R.

26023 AR, 23 H, 27 R, 27 EV, 28.5 AV, 28.5 A, 33.6 UA, 897 B