US 4,879,333 AGrant
Aqueous Pressure Sensitive Adhesive Compositions
Issue Date:1989-11-07
•37 Claims
Abstract
An improved emulsion pressure sensitive adhesive composition is disclosed. The pressure sensitive adhesive composition is formed by emulsion polymerization of vinylic monomers in the presence of a support resin which is added after the polymerization of the monomers has begun.
Metadata
Assignee
- S. C. Johnson & Son, Inc.
Inventor
- Glenn R. Frazee
Application Information
Application Number:US 3162680
Filing Date:1989-02-24
Priority Date:1986-09-09
Art Unit:155
Classifications
IPC:
C08F 216C08K 320
Field of Search:
524526427556;460;457;458203;323208.4
Patent Drawings
This patent does not have any drawings.
Description
The following examples illustrate the practice of the present invention but should not be construed as limiting its scope. All percentages are by weight unless specified otherwise.
EXAMPLE 1
A polymer adhesive composition having the following formulation was prepared:
Part A
329.1 grams deionized water; 12 grams sodium tridecyl ether sulfonate (Sipex EST--30% actives); 3.6 grams octylphenol ethoxylate --10 moles ethylene oxide (Triton X-100).
Part B
0.5 grams acrylic acid; 1.4 grams methylmethacrylate; 8.7 grams butylacrylate; 2.9 gram 2-ethylhexylacrylate.
Part C
2.5 grams ammonium persulfate; 20 grams deionized water.
Part D
10.3 grams acrylic acid; 25.6 grams methylmethacrylate; 165.5 grams butylacrylate; 55.2 grams 2-ethylhexylacrylate.
Part E
57.1 gram deionized water;
Part F
10 grams ammonium hydroxide; 50 grams deionized water;
Part G
180 grams primacor 4983 (a 25% aqueous dispersion with ammonia of copolymer of ethylene with about 20% acrylic acid M.sub.n approximately 20,000 --Dow Chemical Company).
Part H
18 grams methylmethacrylate: 7.2 grams hydroxyethyl methacrylate; 116.1 grams butylacrylate; 38.7 grams 2-ethylhexylacrylate.
The emulsion is prepared by mixing Parts A and B in a reaction vessel which has been purged with nitrogen and is stirred at approximately 200-250 rpm and heated to 80.degree. C. Part C is then added, followed in 5 minutes by the beginning of the Part D primary feed. Part D is fed over a period of 50 minutes. After 1/4 of the Part D feed is in, add Part E. Approximately 15 minutes after the feed of Part D is completed, add Part F over 10 minutes. Immediately after Part F is added, add Part G over a period of approximately 20 minutes, and add Part H over a period of 40 minutes. After all of Part H is in, the material is held for approximately 1 hour at 80.degree. C., cooled and filtered.
The above emulsion has a pH in the range of 8.5-9 and with a non-volatile content of 44-47% by weight and a viscosity of 300-500 centipoise. Generally, the particle size is very fine with no trash particles over 25 microns and very few visible under 25 microns. When it is preferred to have adhesive properties the above emulsion is performed as follows.
The peel tests were performed by pressure Sensitive Tape Council Test PSTC-1 with a residence time, and temperature, as shown in Table I.
The probe tack test was performed as follows: polyken probe Tack (A-1-1) using polyken probe Tack tester from TMI Inc. The Loop Tack Test was performed on an Instron Tensile Tester using a 5" loop of 1" wide tape allowed to contact a stainless steel plate until 1 square inch of tape is on the plate and immediately withdrawn at rate of 12"/minute. Probe Tack 24 hour cure: 648 grams; Tack 1 week Cure 661 grams; probe Tack 1 week cure at 70.degree. C.: 622 grams; Loop Tack 1 week cure: 2.5 pounds.
The shear tests were performed as follows: PSTC-7 with the following configuration: 1/2 by 1 inch contact area with a 1 kg. weight, the long axis orientation was parallel to the applied stress. The results were as follows: 24 hour cure-272 minutes; 1 week cure-325 minutes; 1 week cure at 70.degree. C-greater than 10,000 minutes with no slip.
EXAMPLE 2
The emulsion of Example 2 is prepared by mixing Parts A and B in a reaction vessel which has been purged with nitrogen and is stirred at approximately 200-250 rpm and heated to 80 .degree. C. Part C is then added, followed in 5 minutes by the beginning of the Part D primary feed. Part D is fed over a period of 50 minutes. After 1/4 of the Part D feed is in, add Part E. Approximately 15 minutes after the feed of Part D is completed, add Parts H & I over 10 minutes. Immediately after Parts H & I are added, add Part F over, a period of approximately 20 minutes, and add Part G over a period of 40 minutes. After all of Part G is in, the material is held for approximately 1 hour at 80.degree. C., cooled and filtered.
Part A
324.2 grams water, 18 grams Sipex EST, 9.0 grams Triton X-100.
Part B
2.7 grams styrene, 1.6 grams methacrylic acid; 2.7 grams butylacrylate; 20 grams 2-ethylhexylacrylate.
Part C
2.5 grams ammonium persulfate; 20 grams water.
Part D
24.3 grams styrene, 14.6 grams methacrylic acid; 23 grams butylacrylate, 179.8 grams 2-ethylhexylacrylate.
Part E
57.1 grams deionized water.
Part F 157.5 grams of a resin having a monomer content of 15% styrene. 15% acrylic acid, 70% butylacrylate. a weight average molecular weight of 4,140 and a number average molecular weight 410 prepared using the process of U.S. Pat. No. 4,529,787.
Part G
18 grams styrene, 18 grams butylacrylate, 144 grams 2-ethylhexylacrylate.
Part H
94 grams of water.
Part I
15 grams NH.sub.4 OH.
When tested for peel, shear and tack, the above emulsion gave adequate pressure sensitive adhesive properties.
EXAMPLE 3
Using the procedures of EXAMPLE 1, a pressure-sensitive adhesive emulsion having the following formulation was prepared.
Part A
324.1 grams water, 12 grams Sipex EST, 3.6 grams Triton X-100.
Part B
0.5 grams acrylic acid, 2.7 grams vinyl acetate, 7.7 grams butylacrylate, 2.6 grams 2-ethylhexylacrylate, 0.04 grams ditertiary butyl peroxide.
Part C 2.5 grams ammonium persulfate, 20 grams deionized water.
Part D 10.3 grams acrylic acid, 51.3 grams vinyl acetate, 146.2 grams butylacrylate. 48.7 grams 2-ethylhexylacrylate, 0.66 grams ditertiary butyl peroxide.
Part E 57.1 grams deionized water.
Part F
10 grams NH.sub.4 OH, 50 grams deionized water.
Part G
161 grams Eastman AQ55D, a low molecular weight modified polyester resin available from Eastman Chemical Company molecular weight of 18,000.
Part H
99.6 grams butylacrylate, 34.2 grams 2-ethylhexylacrylate, 7.2 grams hydroxyethyl acrylate, 46 grams vinylacetate.
When tested as in EXAMPLE 1, the above resin had good pressure sensitive adhesive properties.
Comparative Examples
Utilizing a conventional emulsion-polymerization reactor equipped with, among other things, (1) means for adding ingredients into the reactor, (2) means for agitating the reactor contents, (3) means for heating the agitated reactor contents, and (4) means for measuring the temperature of the agitated reactor contents, the following comparative examples, each a polymeric emulsion, were prepared.
EXAMPLE 4
A polymeric resin was produced in accordance with the disclosure of Okamoto et al., as set forth in Japanese Pat. Document No. 47(1972)-606.
The procedure for preparing such a polymeric resin as well as the relative amounts of ingredients utilized to do so are set forth below. All "parts" are parts-by-weight, unless otherwise indicated.
RESIN-PRODUCTION PROCEDURE AND RELATIVE INGREDIENT AMOUNTS
Part J
1200 parts deionized water and 600 parts isopropyl alcohol.
Part K
195 parts acrylic acid monomer, 105 parts styrene monomer, and 1.2 parts Vazo 64 brand (generically known as azo-bis-isobutyronitrile) initiator.
Step 1
Part J was added to a 3-liter reaction flask having appropriate attachments for running the desired reaction. Agitation of the reactor contents as well as nitrogen flow to the reactor was started.
Step 2
After the Vazo 64 brand initiator was dissolved in the monomers identified in Part K, the Part K ingredients were added to the agitated reaction flask.
Step 3
Heat was controllably applied to the reaction flask to obtain a reaction temperature of 65? C. This temperature was maintained for 7 hours,
Step 4
After the agitated, reaction flask contents had been heated for 7 hours at 65.degree. C., the temperature was increased to 80.degree. C. for one additional hour.
Step 5
Following Step 4, the heat to the reaction flask was further increased to begin azeotroping off the isopropyl alcohol as well as any unreacted monomer. The distillate started coming off at 85.degree. C. and was stopped at 95.degree. C. 740 grams of distillate were recovered.
Step 6
Thereafter, the reaction flask was cooled to 80.degree. C. and 162 grams of 28% ammonium hydroxide was added to the agitated reaction flask contents. The resultant mixture was allowed to mix for 1 hour.
Step 7
The mixture was then cooled to 25.degree. C. and thereafter filtered.
The thus-produced polymeric resin solution was utilized, in the following comparative examples, for purposes of attempting to produce acceptable pressure-sensitive adhesives.
PRESSURE-SENSITIVE EMULSION SYNTHESIS
Part L
90 parts of the above resin solution was utilized.
Part M
195.8 parts deionized water, 5.4 parts sodium tridecyl ether sulfate, and 1.6 parts 9-mole ethoxylated octyl-phenol (the latter two being surfactants) were combined.
Part N
10 parts deionized water and 1.13 parts ammonium persulfate were combined.
Part
0 5.1 parts acrylic acid (stabilizer), 818 parts n-butyl acrylate, and 14.4 parts ethyl acrylate (the latter two being monomers) were combined.
Part P
2.3 parts 28% ammonium hydroxide.
Part Q
86.1 parts n-butyl acrylate and 15.2 parts ethyl acrylate were combined.
Step 1
A 1-liter reaction flask having the appropriate attachments was charged with Part M, and heated to 80.degree. C. under a nitrogen flow at 200 RPM agitation. These conditions were maintained throughout the reaction.
Step 2
5.1 parts of part 0 were added to the reaction flask.
Step 3
The reaction flask contents were mixed for 5 minutes.
Step 4
Part N was added to the reaction flask.
Step 5
The reaction flask contents were mixed for 20 minutes.
Step 6
The remainder of Part 0 was fed into the reaction flask at a constant rate over 40 minutes.
Step 7
The reaction flask contents were then mixed for an additional 10 minutes.
Step 8
Part P was then added to the reaction flask.
Step 9
At a constant rate, a 35-minute feed of Part L was fed into the reaction flask. At the same time, a separate feed of Part Q was started at a constant rate over 1 hour.
Step 10
The reaction flask contents were then further mixed for 1 additional hour.
Step 11
The reaction flask contents were thereafter cooled to 25.degree. C. and the finished product was removed from the reaction flask.
EXAMPLE 5
An aliquot of the Example 4 resin was used as "Part L" of the "Emulsion Synthesis" procedure for the production of the emulsion of Example 5, and "Part 0" of the "Emulsion Synthesis" procedure was changed (from what is set out above in Example 4) so as to consist of only 86.1 parts n-butyl acrylate and 15.2 parts ethyl acrylate.
The emulsion produced in accordance with Example 5 thus contained no stabilizer.
EXAMPLE 6
An aliquot of the Example 4 resin was used as "Part L" of the "Emulsion Synthesis" procedure for the production of the emulsion of Example 6; and "Part M" of the "Emulsion Synthesis" procedure was changed (from what is set out above in Example 4) so as to consist of only 195.8 parts deionized water and "Part 0" of the "Emulsion Synthesis" procedure was changed so as to consist of only 86.1 parts n-butyl acrylate and 15.2 parts ethyl acrylate.
The emulsion produced in accordance with Example 6 thus contained neither surfactant nor stabilizer.
TESTING OF ADHESIVE PROPERTIES
After the thus-produced emulsions of each of Examples 4-6 was filtered, the adhesive properties of each such emulsion was then determined as follows.
Adhesive-Testing procedure
A small sample of each such emulsion was placed at the top of a 2-mil thick polyethylene terephthalate (pET) sheet. The PET sheet measured 8"x 11". The sample was then spread over the sheet using a # wire wound rod. The thus-spread sample was then placed in a 120.degree. C. oven for 5 minutes to dry. After the sample was removed from the oven and allowed to cool, a sheet of "Mead R-Coat" brand release liner was placed over the thus-dried emulsion film, thereby forming a construction for further testing. Such a "construction" is hereinafter referred to as a "tape". Test samples that were one-inch wide were then cut from the tape for use in the adhesive-testing procedures, PSTC-1 and Polyken Probe Tacks.
The PSTC-1 values are expressed in ounces per linear inch and the tack values are expressed in grams per square centimeter. Values expressed in ounces per linear inch can b.RTM.converted into pounds per linear inch (pli) by dividing by 16.
The values listed above for the emulsion of Example 4 would indicate that it could be used as a removable pressure-sensitive adhesive (PSA). That is, it removes cleanly, leaving no residue behind (hence the "A" designation following the PSTC-1 numerical value, indicating adhesive failure).
The adhesive values of the emulsion of Example 5, on the other hand, are so low as to indicate that the emulsion of Example 5 could not be utilized as an acceptable PSA. The tape had difficulty adhering to the test panel.
While certain adhesive values of the emulsion of Example 6 appear to indicate high tack, the very low peel strength value (PSTC-1) coupled with a cohesive failure mode (i.e., the "C" designation following the PSTC-1 numerical value) renders it unacceptable as a PSA. Because the peel values of the emulsion of Example 6 possessed so low a cohesive failure value, the film did not possess any internal integrity. Such a film has no presently acceptable application as a PSA.
What has been described herein are novel pressure-sensitive adhesives as well as methods for the production thereof. While the present invention has been described with reference to preferred embodiments, the present invention is not limited thereto. On the contrary, alternatives, changes or modifications may become apparent to those skilled in the art upon reading the foregoing description. Accordingly, such alternatives, changes and modifications are to be considered as forming a part of the invention insofar as they fall within the spirit and scope of the appended claims.
Claims
What I claim is:
1. A method for preparing a reaction mixture which contains an aqueous pressure-sensitive adhesive composition, utilizing an emulsion-polymerization reaction, wherein emulsion particles form upon initiation of the emulsion-polymerization reaction, the method comprising the steps of: combining, in a reactor, initial-feed ingredients comprising water and an emulsion-polymerization surfactant; agitating the reactor contents and subjecting the reactor contents to an inert atmosphere; heating the agitated reactor contents to a predetermined reaction temperature; adding into the agitated reactor monomer-feed ingredients comprising an emulsion-polymerizable monomer mixture and an effective amount of an initiator for initiating the emulsion-polymerization reaction, wherein either the initial-feed ingredients or the monomer-feed ingredients further comprise an effective amount of a stabilizer for preventing coagulation of the emulsion particles; and adding to the agitated reactor, prior to completion of the emulsion-polymerization reaction, an effective amount of a polymeric resin, soluble or dispersible in water or in alkali, and having a number average molecular weight of about 1,000 to about 20,000, for producing in the reactor a reaction mixture containing an aqueous pressure-sensitive adhesive composition having an adhesive value of at least 6.6 ounces per linear inch.
2. The method in accordance with claim 1 wherein the stabilizer is selected from the group consisting of a functional monomer and an ethoxylated alkylphenol having at least 20 ethylene oxide units.
3. The method in accordance with claim 2 wherein the ethoxylated alkylphenol having at least 20 ethylene oxide units is selected from the group consisting of nonylphenol and octylphenol.
4. The method in accordance with claim 2 wherein the functional monomer is selected from the group consisting of acrylic acid, methacrylic acid, and polyethylene glycol monomethacrylate.
5. The method in accordance with claim 1 wherein the stabilizer is present in an amount of about 1 to about 8 percent, based on the weight of the reaction mixture.
6. The method in accordance with claim 5 wherein the stabilizer is present in an amount of about 2 to about 4 weight percent.
7. The method in accordance with claim 1 wherein the emulsion-polymerization surfactant is selected from the group consisting of a nonionic ethoxylated alkylphenol having 15 or less moles of ethylene oxide, an ethylene oxide/propylene oxide block copolymer having less than about 3.5 moles of ethylene oxide and propylene oxide combined, a sodium tridecyl ether sulfonate, and mixtures thereof.
8. The method in accordance with claim 7 wherein the emulsion-polymerization surfactant is present in an amount of about 0.25 to about 5 percent, based on the weight of the reaction mixture.
9. The method in accordance with claim 8 wherein the emulsion-polymerization surfactant is present in an amount of up to about 1 percent, based on the weight of the reaction mixture.
10. The method in accordance with claim 1 wherein the inert atmosphere is nitrogen.
11. The method in accordance with claim 1 wherein the reaction temperature is about 60 to about 100.degree. C.
12. The method in accordance with claim 1 wherein the emulsion-polymerizable monomer mixture comprises 2-ethylhexyl acrylate, butyl acrylate, isooctyl acrylate, lauryl methacrylate, isodecyl acrylate, and mixtures thereof.
13. The method in accordance with claim 1 wherein the emulsion-polymerizable monomer mixture comprises at least one vinylic monomer and divinyl monomers.
14. The method in accordance with claim 1 wherein the emulsion-polymerizable monomer mixture is selected from the group consisting of styrene, alpha-methyl styrene, tetraethylene glycol diacrylate, hydroxyethyl methacrylate, methyl methacrylate, ethyl acrylate, methyl acrylate, propyl acrylate, propyl methacrylate, hexyl acrylate, hexyl methacrylate, vinyl acetate, and combinations thereof.
15. The method in accordance with claim 2 wherein the emulsion-polymerizable monomer mixture comprises methyl methacrylate, butyl acrylate, and 2-ethylhexyl acrylate, and wherein the functional monomer comprises acrylic acid.
16. The method in accordance with claim 2 wherein the emulsion-polymerizable monomer mixture comprises styrene, butyl acrylate, and 2-ethylhexyl acrylate.
17. The method in accordance with claim 16 wherein the functional monomer comprises methacrylic acid.
18. The method in accordance with claim 1 wherein the polymeric resin is either prepared from preselected ethylenically-unsaturated monomers, or said polymeric resin is selected from the group consisting of water-dispersed or water-dispersible aliphatic polyurethanes, water-dispersible copolymers of ethylene and acrylic acid, and water-dispersible polyesters.
19. The method in accordance with claim 18 wherein the ethylenically-unsaturated monomers are selected from the group consisting of olefins, monovinylidene aromatics, alpha,beta-ethylenically unsaturated carboxylic acids and esters thereof, and ethylenically-unsaturated dicarboxylic anhydrides.
20. The method in accordance with claim 1 wherein the polymeric resin is prepared from a monomer selected from the group consisting of at least one vinyl monomer, an ethylene monomer, an ester monomer, a urethane monomer, and combinations thereof.
21. The method in accordance with claim 20 wherein the vinyl monomer utilized to prepare the polymeric resin is selected from the group consisting of acrylic acid including esters and derivatives thereof, methacrylic acid including esters and derivatives thereof, styrene, alpha-methyl styrene, vinyl toluene, and combinations thereof.
22. The method in accordance with claim 1 wherein the polymeric resin is made from ethylene and acrylic acid and has a number average molecular weight of about 20,000.
23. The method in accordance with claim 1 wherein the polymeric resin is a butyl acrylate/acrylic acid/styrene copolymer.
24. The method in accordance with claim 23 wherein said copolymer has a number average molecular weight of about 2,000 to about 2,500.
25. The method in accordance with claim 24 wherein said copolymer has a butyl acrylate/acrylic acid/styrene weight ratio of about 70/15/15.
26. The method in accordance with claim 24 wherein said copolymer has a butyl acrylate/acrylic acid/styrene weight ratio of about 60/25/15.
27. The method in accordance with claim 1 wherein the polymeric resin is added to the agitated reactor when the emulsion-polymerization reaction is about 30 percent to about 50 percent complete.
28. The aqueous pressure-sensitive adhesive composition made in accordance with the method of claim 1.
29. A method for preparing a reaction mixture which contains an aqueous pressure-sensitive adhesive composition, utilizing an emulsion-polymerization reaction, wherein emulsion particles form upon initiation of the emulsion-polymerization reaction, the method comprising the steps of: combining, in a reactor, initial-feed ingredients comprising water and an emulsion-polymerization surfactant; agitating the reactor contents and subjecting the reactor contents to an inert atmosphere; heating the agitated reactor contents to a predetermined reaction temperature; preparing monomer-feed ingredients comprising a first emulsion-polymerizable monomer mixture and a second emulsion-polymerizable monomer mixture, wherein either the initial-feed ingredients or one of the first and second monomer mixtures or both the initial-feed ingredients and said one of the first and second monomer mixtures further comprise an effective amount of a stabilizer for preventing coagulation of the emulsion particles; adding to the agitated reactor a minor portion of said one of the first and second emulsion-polymerizable monomer mixtures; adding to the agitated reactor an effective amount of an initiator for initiating the emulsion-polymerization reaction; adding to the agitated reactor, over a predetermined time period, the remainder of said one of the first and second emulsion-polymerizable monomer mixtures; adding to the agitated reactor an effective amount of a polymeric resin, soluble or dispersible in water or in alkali, and having a number average molecular weight of about 1,000 to about 20,000; adding to the agitated reactor, over a predetermined time period, the other of the first and second emulsion-polymerizable monomer mixtures; and maintaining the agitated reactor contents at the reaction temperature for a predetermined time period, for producing in the reactor a reaction mixture containing an aqueous pressure-sensitive adhesive composition having an adhesive value of at least 6.6 ounces per linear inch.
30. The aqueous pressure-sensitive adhesive composition made in accordance with the method of claim 29.
31. A method for preparing a reaction mixture which contains an aqueous pressure-sensitive adhesive composition, utilizing an emulsion-polymerization reaction, wherein emulsion particles form upon initiation of the emulsion polymerization reaction, the method comprising the steps of: combining, in a reactor, initial-feed ingredients comprising water and an emulsion-polymerization surfactant; agitating the reactor contents and subjecting the reactor contents to an inert atmosphere; heating the agitated reactor contents to a predetermined reaction temperature; adding to the agitated reactor a minor portion of monomer-feed ingredients comprising an emulsion-polymerizable monomer mixture, wherein either the initial-feed ingredients or the monomer-feed ingredients or both the initial-feed ingredients and the monomer-feed ingredients further comprise an effective amount of a stabilizer for preventing coagulation of the emulsion particles; adding to the agitated reactor an effective amount of an initiator for initiating the emulsion-polymerization reaction; adding to the agitated reactor, over a predetermined time period, the remainder of the emulsion-polymerizable monomer mixture; adding to the agitated reactor, prior to completion of the emulsion-polymerization reaction, an effective amount of a polymeric resin, soluble or dispersible in water or in alkali, wherein the number average molecular weight of the polymeric resin is about 1,000 to about 20,000; and maintaining the agitated reactor contents at the reaction temperature for a predetermined time period, for producing in the reactor a reaction mixture containing an aqueous pressure-sensitive adhesive composition having an adhesive value of at least 6.6 ounces per linear inch.
32. The aqueous pressure-sensitive adhesive composition made in accordance with the method of claim 31.
33. The method in accordance with claim 1 wherein the polymeric resin is co-fed into the agitated reactor along with a portion of the emulsion-polymerizable monomer mixture.
34. The method in accordance with claim 29 wherein at least a portion of the polymeric resin is co-fed into the agitated reactor along with at least a portion of said other of the first and second emulsion-polymerizable monomer mixtures.
35. The method in accordance with claim 31 wherein at least a portion of the polymeric resin is co-fed into the agitated reactor along with at least a portion of the remainder of the monomer-feed ingredients.
36. The method in accordance with claim 29 wherein the monomeric makeup of the first emulsion-polymerizable monomer mixture is different from the monomeric makeup of the second emulsion-polymerizable monomer mixture.
37. The aqueous pressure-sensitive adhesive composition made in accordance with the method of claim 36.
Patent Citations (9)
Non-Patent Literature (1)
- Advances in Chemistry Series 125--ACS, (1973), Washington, D.C. by Nakajima, pp. 98-107.