CA1074037A - Remoistening adhesive composition and adhesive sheet - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A remoistening adhesive composition based on high amylopectin, low amylore starch includes poly(vinyl methyl ether-maleic acid monoalkyl ester) in a preferred proportion of about 1.5-20% by weight of the composition, thereby providing improved quick tack and shorter bonding times.
An adhesive sheet comprises a sheet of paper coated on one side thereof with the composition.

Description

1 Thls inventlon relates to remolstenlng adhesive

2 composltlons and to adhesive sheet~. More partlcularly,

3 the lnventlon relates to lmproved remoistening adheslve

4 composltions based on hlgh amylopectin, low amylose starch and to adhesive sheets prepared therewith.
6 Remoistening adheslve composltions based on hlgh 7 amylopectin, low amylose starch are disclosed ln U. S, 8 Patents Nos. 2,791,512 and 2,997,404. The adheslve 9 compositions are useful for the manufacture of adhesive sheets including adhesive tape.
11 High ~peed packaglng imposes requirements oi high 12 initial tack and relatively short bonding time for the -~
13 utilization of remoistening adhesives on adhesive sheets, 14 particularly, reini'orced adhesive tapes. It would be advantageous lf improvement~ ln these propertles could be 16 achieved, over the results obtalned with the prlor composltlons.
17 It has now been dlscovered ln accordance wlth the 18 lnvention that a remoi~tening adhesive composition based on 19 high amylopectin, low amylose starch, having high lnitial tack coupled with significan,t decrease in the time necessary 21 for the formatlon of a permanent bond, is provided by ln-22 corporating in the composition the polymer, poly(vinyl methyl 23 ether-maleic acid monoalkyl ester), in a minor, effective 24 amount.
The improvements of the invention are exhlblted by a 26 twc-co~ponent system o~ the starch and the polymer. In practlc~, 27 however, lt ls generally preferred to incorporate additives, as 28 conventionslly employed in such starch compositions, for con-29 tributing deslrable propertles and/or reduclng costs. Such .. , ~
' . ', ~

' 1074a 37 l addltlves lnclude viscosity-reducing agents, antlcurling 2 agents, and wetting, film-formlng or tackifylng agents.
3 Starches high in amylopectln and low ln amylose 4 are readlly avallable, preferably beln~ derived from the waxy malze strain oi' corn, and also from other sources.
6 The preferred products contain up to about 10% amylose, by 7 welght, and the balance substantially amylopectln, and 8 available products contain ~rom 2-10% amylose. Commercially 9 avallable starch products suitable for use ln the adhesive . ~ ~
10. ~ composltion include "Amaizo" (American ~laize Products Company), 11 "Tapon" (National Starch and Chemical Corporation), ''Sta-Tape"
12 (A. E. Staley Manufacturing Company), and "Gum Tac" (Corn 13 Product6 Corporation). The starch preferably is employed in 14 a minimum proportion of about 60~, and ln a proportlon in a range of about 60 to 90~, in proportions by weight of the lff composltion, on a sollds or dry basls.
17 Poly(vinyl methyl ether-maleic acid monoalkyl ester) 18 ls a copolymer of the followlng structural formula, whereln l9 R represents an alkyl radical and n!represents the number oi' repetitlve unlt~ in the polymer:

21 f-CH3 22 - -CH2 CH - CH fH -23 C~0 C~0 2S _ ~ 0-R n 26 The lower alkyl esters are pre~erred, especially those ln 27 which the alkyl radical, R, has 1-4 carbon atoms. ~ore 28 preferably, tbe alkyl radical is methyl, ethyl, lsopropyl, 29 or n-butyl, and the speclfic vlscosity of the polymer as .

.i :, ~, .

1 determined on a solution of 1 ~ram thereoI in 100 ml. oi' 2 methanol at 25C (determined with reference to methanol o~
3 25C) is approximately as follows:

4 Alkyl Radical Speci~ic Yisco~ity Methyl 0.9-1.3 6 Ethyl ` 1.1-1.5 7 I~opropyl 1.3-1.7 8 n-Butyl 1.6-2.0 ~ .
9 The polymer, poly(vinyl methyl ether-maleic acid monoalkyl ester), is employed in a minor amount effective 11 to increase the initial tack and decrease the bondin~ time 12 as compared to the composition in the absence of the polymer.
13 The proportion may vary with the 6peclfic polymer and with 14 Yariations in the in~redients of the adhesive composition.
In ~eneral, the polymer is effective in a proportlon of 16 about 1.5-20%, preferably about 1.5-12.5%, in proportions 17 by weight o~ the composition, on a solids or dry basis.
18 As in the case of the prior remoistening adhesive 19 compositions, dextrin may be lncorporated in the adhesive ~0 composition of the invention. Dextrin reduces viscosities 21 and costs, and also performs a wetting function. White corn 22 dextrin and canary dextrin are prei'erred. Suitable commercially 2 ~ ' avallable products include the "Globe" white corn a~d canary 24 dextrins (Corn Products Corporation); and the "Nadex" white 2S corn and canary dextrins (National Starch and Chemical Corp-26 oration), Dextrin may be employed in a proportion up to 27 about 20%, preferably in the range of about 5-20%, in . , . .
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1 proportions by wei~ht of the composition, on a sollds 2 basis. The dextrin may contain up to about 35% amylose 3 by wei~ht, and the foregolng products contain about 25-35%
4 by weight of amylose and the balance substantially amylo-pectin. It is preferred to maintain the amylose content 6 of the complete adhesive composition below about 18%, by 7 weight, on a solids basis.
8 Anticurling agents as conventionally employed in 9 the remoistening adhesive art may be included in the new adhesive composition. Such a~ents include sodium nitrate, 11 urea, sorbitol, and others. ~n anticurling agent may be 12 included in a proportion up to about 15%, preferably in the 13 range of about 5-15%, by weight of the composition, on a 14 solids basis.
Wetting, film-forming, or tackifying agents 16 (gene1ally referred to hereinafter as "wettin~ agents") as 17 also conventionally employed in the remoistenin~ adhesive 18 art, serving to increase worklng or!open times, li~ewls~
19 may be included in the new adhesive compositlon. Such agents include, for example, polyacrylamide, calcium 21 chlor~de, zlnc chloride, trisodium phosphate, and soap 22 chips. Such a wetting agent may be included in a proportlon 23 up to about 5%, preferably in the range oi about 0.5-5%, by 24 weight of the composition on a solids basi~. -The adhesive compositlon is provided in the form o~
26 an aqueous solution for coating purposes. The compon~nts are 27 slurried in water, with the poly(vinyl methyl ether-maleic 28 acid monoalkyl ester) dissolved in a polar solvent for 29 incorporation in the solution. Suf~iclent water is lncor-porsted in the solution to produce a coating solutlon ! . . .
::
' ' ' " ' ' ' ' , ' , . ' ' ~ . , . ' ' ' . . ;
'' , . ., ' ' . , ' , -1 vlscoslty preferably of about 250-3,000 centipoises at 2 80C, corresponding to a sollds content of about 35-60%
3 by weight of the solution. Suitable solvents for the 4 polymer include water-soluble alcohols, ketones and esters of boiling points lower than about 95C, includin~ methanol, 6 ethanol, isopropanol, acetone, diethylene glycol, ethylene 7 glycol monomethyl ether, tetrahydrofuran, ethyl acetate, 8 butyl carbitol, butyrolactone, methyl ethyl ketone, dioxane, 9 and others. The aqueous composition is gelatinized at elevated temperature, coated on a suitable substrate, such 11 as paper, and dried to about 5% maximum retained moisture, 12 all following conventional procedures.
13 Adhesive sheets produced in the foregoing manner 14 according to the invention, especially reinforced tapes, exhibit significantly hi~her initial tack generally 16 accompanied by significant decrease in bonding tlme, as 17 compared to the prior composltlons. The improved results 18 according to the invention are illustrated in the examples 19 which ~ollow. In the examples, the adhesiveness of gummed tape samples ls measured using the ~IcLaurin tack tester as 21 in ASTM deslgnation D-773-47. The adhesive is coated on 22 two-inch wide test strips o~ 60 pound basis kraft paper 23 at a coating weight of 14 pounds per 3,000 square feet.
24 Bonding times are determined after i'ive seconds of open tlme following moistenin~, a6 the measure of time in ~econds 26 for the moistened adheslve strip which has been la~lnated to 27 a standard No. 200 corrugate substrate to pull paper fibers 28 from the ~ub~trate when pulled bac~ upon it~elf. Times are 29 measured to inltial fiber tear and to full fiber tear.

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; : - ,~ . ' 1 The following examples lllustrate the preparation 2 of adhesive compositlons containing the polymer, poly(Yinyl 3 methyl ether-malcic acid monoalkyl ester) accordin~ to the 4 invention, and the improved results obtained therewith, as compared to adhesive compositions not containing the polymer.
6 It will be understood that the invention is not limited to 7 the examples, which are merely illustrative, or to the 8 materials, proportions, conditions and procedures set forth 9 therein, In the examples, the proportions are by weight.

Example 1 11 In the manufacture of an adhesive solution for 12 coating purposes according to the invention, 4,6 parts 13 white corn dextrin ("Globe Dextrine"), 1.4 parts oi' poly-14 B acrylamide ("Cyanamer P-26", mol. wt. 200,000, American Cyanamid Company), and 46 parts of water are slurried for 16 five mlnutes. The dextrin contains approximately 27% amylose 17 and 73% amylopectin.
18 To the slurry is added 56 parts of corn starch 19 ("Tapon") containing 6% of amylose and the balance substan-tially amylopectin. The temperature is raised to 70C, and 21 1.4 par`ts of poly(vinyl methyl ether-maleic acld mono-n-butyl 22 ester) (specii'ic viscosity 1,8, "Gantrez ES", G.A.F. Corporation) 23 in S0~ solution in methanol is added and mixed for five mlnutes.
24 The slurry then is heated to 95C and gelatlnized b~
cooking at that temperature for 15 minutes, during which time, 26 the methanol solvent for the polymer is substantially distilled 27 off. Anhydrous calclum chloride, 0.7 parts, is added with 28 mixing, to complete the preparation of the adhesive coating ~f~-1 solution. The 601ution contain~ 54% solids and has a 2 viscosity of 800 centlpoises at 80C. It ha6 the follow-3 ing composition, ln percentages by welght, on a solids or 4 dxy basls:

S Material Proportlon, %
6 Starch 85.0 7 Dextrin 8.5 8 Polyacrylamide 2.6 9 Poly(vinyl methyl ether-maleic acid mono-n-butyl 11 ester) 2.6 12 Calcium chloride 1.3 .:
13 The adhesive solution i8 coated on paper sheets or strips 14 ln the conventional manner and dried to about 5~ maximum retained moisture.
16 Gummed tape samples tested on the McLaurln tack 17 tester exhibit adhesivity values o~ about 65. Bondlng tlmes 18 with 5 seconds open time are: Inltial ~iber tear, 8 seconds;
19 full flber tear, 13 seconds.
The monomethyl, monoethyl, or monoisopropyl ester 21 of poly(vinyl methyl ether-malelc acid) may be substituted 22 for the monobutyl ester thereof in the above compositlon, 23 in the same proportion.
2~ A composltion formulated in the same manner and ~rom the same materlals as and comparable to the above 26 composition but containing no ester of poly(vinyl methyl 27 etber-maleic acid) includes the following materials, in ~.
., l ' ' j 107403 ~

1 percentages by weight, on a sollds-basis:

2 ~aterial Proportion, %
3 Starch 87.3 4 Dextrin 8.8 Poly~crylamide 2.6 6 Calcium chloride 1.3 7 Gummed tape samples tested on the McLaurin tack tester 8 exhibit adhesivity values of about 32. Bonding times with 9 5 seconds open time are: Initial fiber tear, 15 seconds;
full flber tear, 22 seconds.
11 Another pre~erred composition according to the 12 ` . invention has the i`ollowing composition, employing the 13 same materials as ln the first-described composition.

Material . Proportion, %
..
16 Starch ! . 85.0 17 Dextrin 8.5 18 Polyacrylamide 2.5 19 Polytvinyl methyl ether-maleic acid mono-n-butyl 21 ~ ester) 2.5 22 ` Calcium chloride 1.5 23 Example 2 24 The following composition6 are formulated with water, heated and ~elatinized in the manner of Example 1, 26 to provide adhesive solutions containing 38% sollds:

.
- . . ., .' : :: ' ... . ~ . .

.
1 Material Proportion, %
2 Compositlon A
3 Starch ("Tapon") 83.2 4 Sodium nitrate 12.3 ` Polyacrylamide (M.W. 200,000 4.5 6 ` Composition B
7 Starch ("Tapon") 83.2 8 Sodium nitrate 12.3 9 ` Polyacrylamide (M.~'. 200,000) 2.25 Poly(vinyl methyl ether-maleic 11 acid mono-n-butyl ester) 12 (sp. vis.1.g), 50% in methanol 2.25 13 Com_ositlon C
14 Starch ("Tapon") 79.1 Sodium nitrate 12.4 16 Polyacrylamide (M.lV. 200,000) 2.2 17 Poly(vinyl methyl ether-maleic 18 acid mono-n-butyl ester) 19 . (6p. vi6. 1.8), 50% in methanol 6.3 Compositions D, E, and F are the same as Composition 21 B, with the~ substitution, respectively, of the monomethyl 22 ester (sp. vis. 1.1), the monoethyl ester (sp. vis. 1.3), and 23 the monoisopropyl ester (sp, vis. 1.5) of poly(vinyl methyl 24 ether-maleic acid) for the butyl ester thereof. Each of the esterfi is incorporated in the adhesive solu~ion as a 50%
26 solution in methanol.
27 The McLaurin adhesivities and bonding times with 28 5 seconds open time, includlng lnltlal i'iber tear and full _ 9 _ , '.

.. . . ~ , ~

1~74037 1 fiber tear, obtained with the compositions are set forth 2 in the following table:

3 . Composition Adhesivity Initial Tear, secs. Full Tear, secs.
.

6 C ~8 7 12 9 F 40 . 6 8 Example 3 11 . The following adhesive compositions are formulated 12 with water, heated and gelatinized, generally in the manner 13 oi' Example l, to provide adhesive solutions containing 40%
14 solids:
Material . _roportionl %
16 Composition G
17 Starch ("Tapon") 92.5 :
18 Sodium nitrate 7.5 19 . Composition H
Starch~("Tapon') 87.5 21 Sodium nitrate 7.5 22 Poly(vinyl methyl 23 ether-malelc acid 24 mono-n-butyl ester) 5.0 The ~cLaurin adhesivitie6 and bonding tlmes with 26 5 secorld~ open tlme, including initial fiber tear and full 27 i'iber tear, obtain~d with the compositions are ~et forth ln 28 the follo~ing table:

.: , . .:

107403~7~

.
Compositioll Adhesivity Initlal Tear, secs. Full Tear, secs.

. ~ ;

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Claims (12)

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

1. In a remoistening adhesive composition based on high amylopectin, low amylose starch, the improved combination with poly(vinyl methyl ether-maleic acid monoalkyl ester), in an amount of 1.5-20% in proportion by weight of the composition on a solids basis and effective to increase the in-itial tack and decrease the bonding time of the composition.

2. A composition as defined in claim 1, and wherein said alkyl radical has 1-4 carbon atoms.

3. A composition as defined in claim 1, wherein said alkyl radical is methyl, ethyl, isopropyl, or n-butyl, and the specific viscosity of said polymer as determined on a solution of 1 gram thereof in 100 ml. of methanol at 25°C.
is approximately as follows:

Alkyl Radical Specific Viscosity Methyl 0.9-1.3 Ethyl 1.1-1.5 Isopropyl 1.3-1.7 n-Butyl 1.6-2.0

4. A composition as defined in claim 1 and wherein said starch is present in a minimum proportion of about 60%
by weight of the composition, on a solids basis.

5. A composition as defined in claim 4 and wherein said starch contains up to about 10% amylose by weight and the balance substantially amylopectin.

6. A composition as defined in claim 5 and wherein the amylose content of the composition is below about 18% by weight, on a solids basis.

7. A remoistening adhesive composition which comprises, in approximate percentages by weight:

Dextrin up to 20%
Anticurling agent up to 15%
Wetting agent up to 5%
Poly(vinyl methyl ether-maleic acid monoalkyl ester) 1.5 to 20%
Starch Balance said dextrin being white corn dextrin or canary dextrin containing up to about 35% amylose by weight, said alkyl radical having 1-4 carbon atoms, and said starch containing up to about 10% amylose by weight and the balance substantially amylopectin, the minimum proportion of said starch being about 60% by weight.

8. A composition as defined in claim 7 and wherein said alkyl radical is methyl, ethyl, isopropyl, or n-butyl, and the specific viscosity of said polymer as determined on a solution of 1 gram thereof in 100 ml. of methanol at 25°C is approximately as follows:

Alkyl Radical Specific Viscosity Methyl 0.9-1.3 Ethyl 1.1-1.5 Isopropyl 1.3-1.7 n-Butyl l.6-2.0

9. A composition as defined in claim 8 and containing about 5-20% dextrin, about 5-15% anticurling agent, and about 0.5-5% wetting agent, in percentages by weight.

14 11. A remoistenlng adhesive compositlon which comprises, ln approximate percentages by weight:

White corn dextrin 8.5%
Polyacrylamide 2.5-2.6%
Calcium chloride 1.3-1.5%
Poly(vinyl methyl ether-maleic acid n-butyl ester) 2.5-2.6%
Starch 85.0%

said dextrin containing about 25-35% amylose by weight, said starch containing up to about 10% amylose and the balance substantially amylopectin, and said poly(vinyl methyl ether-maleic acid n-butyl ester) having a specific viscosity of about 1.6-2.0 as determined on a solution of 1 gram thereof in 100 ml. of methanol at 25°C.

11. An adhesive sheet which comprises a sheet of paper coated on one slde thereof with a compositlon as defined in claim 1.

12. hn adhesive tape which comprises a flexible elongated paper strip coated on one side thereof wlth a composition as defined in claim 1.