PRESSURE-SENSITIVE ADHESIVES BASED ON SIMILAR POLYMERS

Abstract: A pressure-sensitive adhesive is formed from a high-molecular-weight alkyl acrylate polymer with from 2 to about 4 carbon atoms on the alkyl side chain, and is plasticized by an essentially-liquid, low-molecular-weight alkyl acrylate polymer, which polymers preferably have identical monomer contents.

Description: PRESSURE-SENSITIVE ADHESIVES BASED ON SIMILAR POLYMERS Background of the Invention A pressure-sensitive adhesive should be soft so that it can develop sufficient interfacial contact area with a substrate on. application of very light pressure. It must, however, also be strong enough to resist debonding failure. Conventionally, this rate-dependent viscoelastic property of pressure-sensitive adhesives was achieved by blending tackifying resins with a rubber-based polymer. More recently, there has been an increased interest in using polyacrylates as pressure-sensitive adhesives for their superior weathering and- aging properties. There are, however, some disadvantages for the acrylic pressure- sensitive adhesives: the material cost of the acrylates is higher than the conventional rubber-based adhesive, and tack performance is normally lower. It is difficult to find good tackifiers that are commercially available for acrylic adhesives. When a porous material such as paper is used as the facestock, many compounded acrylic adhesives are prone to have certain components "bleed" out and stain the facestock. In 1964 Wetzel presented a model of a compoundable pressure-sensitive adhesive based on a resin and a sticky low-molecular-weight rubber in which a sticky low-molecu¬ lar-weight tackifier was dispersed in the bulk of the base resin. Solid tackifiers have since been conventionally employed to induce pressure-sensitive characteristics to a base polymer. The effect of tackifier addition is shown in FIG. 1, attached hereto. The present invention is based on a different formu- lation approach to pressure-sensitive adhesives. The technique allows the use of low-cost materials to form acrylic pressure-sensitive adhesives. The formulation is highly compatible with, and will not stain, the paper facestock. When a certain percentage of acid function- ality is incorporated in the formulation, the novel adhesives can be removed easily from the substrate when the alkaline solution is applied. Summary of the Invention The present invention is directed to compatible mixtures of low- and high-molecular-weight alkyl acrylate polymers which in themselves are not pressure-sensitive adhesives, but which form pressure-sensitive adhesives when combined. In particular, the pressure-sensitive-adhesive com¬ positions are comprised of a high-molecular-weight alkyl acrylate polymer having a molecular-weight of greater than at least 10 times the entanglement molecular-weight, and containing at least about 70 percent by weight of an alkyl acrylate containing from 2 to about 4 carbon atoms on the alkyl side chain, preferably at least 90 percent by weight of said alkyl acrylate, with a lower molecular- weight polymer having a molecular-weight which is less than 2 times the entanglement molecular-weight, and also containing at least 70 percent, preferably at least 80 percent, by weight of the same alkyl acrylate. The use of copolymers is preferred. However, the polymers may differ in comonomer content by no more than about 10 percent by weight. The presently preferred alkyl acrylate is ethyl acrylate and, while any copolymerizable comonomer can be used to modify the properties of the polymers employed, it is preferred to use an unsaturated carboxylic acid, preferably acrylic acid, to enable crosslinking to modify adhesive properties. The low-molecular-weight alkyl acrylate polymer is present in a concentration of from about 40 percent to about 80 percent by weight, based on the mixture of high- and low-molecular-weight alkyl acrylate polymers. By combining the two highly similar polymers, one can obtain without loss of compatibility a wide range of adhesive properties and applications. In addition, alkali removability is feasible for the formed pressure- sensitive adhesives for an acid content of from about 5 percent to about 30 or more percent by weight. Glass- transition temperature of the mixed polymers with addi¬ tives is at least about 40°C below the use temperature. Brief Description of the Drawings FIG. 1 is a plot of the log of the shear modulus (Log G) or the log of the ratio of shear stress over shear strain vs. frequency of deformation (Log ω ) for a base resin (solid line) modified by a tackifier system to form a pressure-sensitive adhesive of desired properties (dashed line). FIG. 2 shows, on the same scale as FIG. 1, the formu- lation of a pressure-sensitive adhesive by plasticizing a high-molecular-weight alkyl acrylate polymer with a low- molecular-weight alkyl acrylate polymer. Detailed Description According to the present invention there are pro¬ vided pressure-sensitive adhesives based on a mixture of elastomeric, high-molecular-weight alkyl acrylate polymers and essentially liquid, low-molecular-weight alkyl acrylate polymers of ' identical or differing comonomeric content, which in combination form low-cost pressure-sensitive adhesives having a wide variety of properties, including aggressive adhesion to polyethylene substrates and, when containing a copolymerized carboxylic acid, alkali removability. The pressure-sensitive adhesives of the invention comprise, in admixture, an alkyl acrylate homopolymer containing from about 70 percent to about 100 percent by weight polymerized alkyl acrylate in which the carbon content of the alkyl side chain portion of the acrylate is from 2 to about 4 carbon atoms. The high-molecular- weight alkyl acrylate polymer preferably contains from about 90 percent to about 100 percent by weight of the alkyl acrylate and has a molecular weight of at least 10 times the entanglement molecular-weight. Stated another way, it must have a weight-average molecular-weight (Mw) of at least 10*5, normally from, about lϋ 5 to about 5 x 10*5. "Entanglement molecular-weight" as used herein, is defined in Viscoelastic Properties of Polymers, 3rd Edition, John D. Ferry, John Wiley and Sons, 1981, incorporated herein by reference. The second component is a low-molecular-weight, gen- erally liquid alkyl acrylate polymer in which the alkyl portion is the same as that of the high-molecular-weight alkyl acrylate polymer. The second alkyl acrylate polymer has a molecular-weight which is less than 2 times the entanglement molecular-weight, and/or a weight-average molecular-weight of less than about 2 x 10^, or less than l about 20,000. As with the high-molecular-weight alkyl acrylate polymer, from 0 percent to about 30 percent, preferably from 0 percent to about 10 percent, of the low-molecular-weight polymer may be one or more other 5 comonomer(s) , with the proviso that the comonomer content of the high-molecular-weight alkyl acrylate polymer does not differ from the comonomer content of the low-molecu¬ lar-weight alkyl acrylate polymer by more than about 10 percent by weight. Any comonomer that is polymerizable 10 with an alkyl acrylate can be employed. There may be mentioned aromatic monomers such as styrene; unsaturated carboxylic acids containing from 2 to about 6 carbon atoms, such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid; acrylates, such as 15 methyl acrylate and 2-ethylhexyl acrylate; and methacry- lates, such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, and the like. The comonomer content may..be the same or totally different in terms of the high-molecular-weight alkyl acrylate polymer as compared 0 to the low-molecular-weight alkyl acrylate polymer. There may be included other ingredients, such as anti- oxidants, colorants, UV absorbents, and the like. In the conventional pressure-sensitive-adhesive system, a tackifier -system is employed to modify proper- 5 ties of the base resin, and acts to raise the glass- transition temperature and to lower the rubber-plateau modulus of the base resin. This is shown in Fig. 1, wherein the solid line is the base resin and the dashed line is the desired pressure-sensitive adhesive (PSA). Q In the practice of the instant invention and with reference to FIG. 2, the low-molecular-weight polymer acts as a plasticizer which lowers the glass-transition temperature and rubber plateau of the base resin (solid line), to adhere the desired master curve (dashed line) = for the pressure-sensitive adhesive. . The amount of low-molecular-weight alkyl acrylate polymer added will depend on the nature of the high- molecular-weight alkyl acrylate polymer and the pressure- sensitive-adhesive properties desired. Generally, the low-molecular-weight alkyl acrylate polymer will be pre¬ sent in an amount of from about 40 percent to about 80 percent by weight, based on the total weight of the alkyl acrylate polymers. The components of pressure-sensitive-adhesive formu¬ lations of the instant invention are formed by emulsion polymerization. The means employed are, in the main, conventional. The determination as to whether the product of emulsion polymerization will be a high-molecular- weight alkyl acrylate polymer or a low-molecular-weight alkyl acrylate polymer, is by inclusion of a chain trans¬ fer agent such as n-dodecyl mercaptan (n-DDM). The chain transfer agent may be present in an amount up to about 10 percent by weight or more of the emulsion monomer system. Surfactants can modify the distribution of molecular weights from broad to narrow. Besides separate formulation of the pressure-sensi¬ tive adhesives of this invention from an individually polymerized high-molecular-weight alkyl acrylate polymer and a low-molecular-weight alkyl acrylate polymer, and the polymerization of a mixture of monomers, emulsion polymer¬ ization can be conducted by initially polymerizing the high-molecular-weight polymer in the absence of a chain transfer agent to a desired solids level; and then by the inclusion in the polymerization system of a chain transfer agent to induce limitations on the molecular weight of the polymeric chain in continued polymerization, to form an in situ mixture of high-molecular-weight alkyl acrylate polymers and low-molecular-weight alkyl acrylate polymers which, on deposition from the emulsion onto a face stock, provide a pressure-sensitive adhesive. The compositions of this invention uniquely enable the adhesive coating of porous facestocks without bleed, have wet-stick characteristics, namely, the ability to adhere to surfaces on which moisture has condensed and which contain carboxylic-acid moieties, and have the ability to be readily removed from a substrate by alkaline cleaning solutions and caustic solutions. While nowise limiting, the following Examples are illustrative of the invention. "P" means panel failure; "C" means cohesive failure; H ιpτ" means immediate paper tear; "PS" means panel stain; "SPS" means slight panel stain; "ks" means kiloseconds; "F" means fail; and "PE" means polyethylene. Test methods utilized were as follows: molecular weight distribution by ASTM D-3536-76, ASTM D-3590-68 and ASTM E-682-79; shear by ASTM D-3654-78 and D-1000-68 and PSTC (Pressure-Sensitive Tape Council) Test #7, 6th Edition; 90° peel by PSTC Test #2, 5th Edition; loop tack by PSTC Test #7, 6th Edition; mandrel by ASTM D-3654-78 and D-1000-68. Vellum 80 was used as a facestock because it is highly absorbant and amplifies bleed. Examples 1 to 10 There were formed by emulsion polymerization, homopolymers of ethyl acrylate to provide a feasibility evaluation of the ability to form pressure-sensitive adhesives from high-molecular-weight and low-molecular- weight homopolymers of ethyl acrylate. Examples 1 to 3 disclose the formation of high-molecular-weight elasto- meric resins, and Examples 5 to 7 disclose the formation of low-molecular-weight resins. Example 4 is a transi¬ tional example, showing the formation of a resin of reduced molecular weight as a consequence of the intro¬ duction of a small quantity of n-dodecyl mercaptan (n-DDM) as a chain transfer agent. The polymerization conditions and polymer properties are shown in Table I. Solids content after polymerization was about 50 percent by weight. Table II shows the performance properties of mixtures of the polymers of Example 2 and Example 7. Examples 11 to 24 While the results of Examples 1 to 10 establish the feasibility of the use of polyethyl acrylate homopolymers, in the formation of general-purpose pressure-sensitive adhesives from materials which would otherwise not have pressure-sensitive adhesive characteristics, it was deter¬ mined to use a carboxylic acid as part of the emulsion polymerization system to form adhesives of varying proper¬ ties, as a consequence of not only acid content but of the use of a crosslinking agent as well. The carboxylic acid employed was acrylic acid. In Table III, Examples 11 to 16 show, respectively, the conditions for the formation of high- and low-molecular-weight ethyl aerylate/acrylic acid copolymers having 10 percent, 6 percent, and 2 per- cent by weight acrylic acid. Table IV, Examples 17 to 24, shows the adhesive properties of combinations of the polymers formed in Examples 11 to 16. In preparation of the polymers, 50 parts of the pre-emulsion was added to a reactor charge at 40°C and, while that temperature was maintained, the balance was added over 60 minutes. Heat¬ ing continued for 30 minutes at 60°C. Five parts of the accelerator were added to the reactor charge and the balance to the pre-emulsion. - t t cn OJ o o Oi TABLE I Examples 1 to 7 EXAMPLES Monomer, pts Ethyl Acrylate 100 100 100 100 100 Surfactant N-lli 1 3.6 X-2ϋθ2 3.4 CO-4363 (60% solids ) 4.3 OO-730* (60% solids) — ~" — 5.7 5.7 Buffer (NH 4 )2θ0 3 .21 .14 .14 .14 .14 Initiator (NH 4 )2S2θ8 .28 .28 .14 .57 .57 t-BHP 5 - .28 .28 .57 .57 AWC 6 .28 .28 .28 .29 .29 I Fe 3 +EDTA Trace Trace Trace Trace Trace h-> O Chain Transfer n-DEM None None None .57 1.50 Monomer Pre- Pre- Pre- Pre- POLYMERIZATION CONDITIONS Feed finulsion Etaulsion E-iulsion Einulsion Reactor Temperature, °K 308-318 333 333 308-313 308-313 Jacket Temperature, °K 293-298 313 313 293 293 Peed Time, ks 3.6 3.6 3.6 2.7 2.7 Cook-Off Time, ks 1.8 1.8 1.8 1.8 1.8 Cook-Off Temperature, °K 323 333 333 323 323 68 x 10 5 2.61 x 10 5 4.10 x 10 5 1.01 x 10 5 4.4 x lθ4 Distribution Coefficient (Mw/Mn) 3.4 8.1 4.6 8.1 3.2 % Below 20,000 2.2 32.3 3.6 41.0 55.0 1 a nonionic surfactant manufactured and sold by Rohm and Haas 2 an anionic/nonionic surfactant manufactured and sold by Rohm and Haas 3, 4 an ethoxylated alkyl phenol surfactant manufactured and sold by GAF 5 tert-butyl hydrqperoxide 6 sodium formaldehyde sulfoxylate TABLE I (Cont'd.) TABLE II Examples 1 to 7 Examples 8 to 10 Synthes Ls of Polyethylacrylate Homopolymers EXAMPLES 6 7 8 9 10 Monomer, pts Blend, Ethyl Acrylate 100 100 Ex. 2/Ex. 7 60/40 50/50 40/60 Surfactant Facestock Vellum 80 Vellum 80 Vellum N-111 X-200 Coat Weight g/m 2 24 g. 24 g. 24 g CO-436 CO-730 5.7 5.7 Quick Stick Buffer Recycled (NH 4 ) 2 Cθ 3 .14 .14 Cardboard Good Good Good Initiator Poly¬ (MH4) 2 S 2 θ 8 .57 .57 ethylene Good Good Good t-BHP .57 .57 0.500 kg AWC .29 .29 Shear, ks (NA) 0.1(C) (NA) Fe 3 +EDTA Trace Trace 90° Peel Chain Transfer (N/m) 208(P) 172(P) 156(P) n-DDM 5.00 10.00 Monomer Pre- POLYMERIZATION CONDITIONS Feed Emulsion Reactor Temperature, °K 328 328 Jacket Temperature, °K 313 313 Feed Time, ks 3.6 3.6 Coo -Off Time, ks 1.8 1.8 Cook-Off Temperature , °κ 333 333 Mw 2 .15 x 10 4 1. 78 x 10 4 MWD 2.3 2.3 % Below 20,000 28.0 21.0 ro Ol o to 01 o Ol Ol TABLE I I I EXAMPLE 11 12 13 14 15 16 Reactor Charge 00 200 200 200 200 200 CO-436 (60%) 1.0 1.0 1.0 1.0 1.0 1.0 Fe 3 +EDTA 0.1 0.1 0.1 0.1 0.1 0.1 a2 2°7 1.0 1.0 1.0 1.0 1.0 1.0 (NH 4 ) 2 C0 3 1.5 1.5 1.5 1.5 1.5 1.5 {NH 4 ) 2 S 2 O a 4.0 4.0 4.0 - - - Pre-Emulsion H 2 0 300 300 300 300 300 300 CO-436 (60%) 20 20 20 20 20 20 TREM-L-40 (40%)7 10 10 10 10 10 10 Ethyl Acrylate 630 648 606 630 648 686 Acrylic Acid 70 52 14 70 52 14 to Dodecyl Mercaptan 70 70 70 I t-BHP 4. 0 4. 4.0 1.0 1.0 1.0 Accelerator H 2 0 100 100 100 100 100 100 AWC 2.0 2.0 2.0 2.0 2.0 2.0 Product Solids 8% 55 55.2 55.5 52.7 53.1 53.1 Viscosity, CPS 410 1950 1000 . 2300 P H 4.2 5.0 5.1 6.3 Mw 1.0 x 104 1.1 x 104 1.3 x 104 4.8 x 10-** 5.7 x 105 3.2 x 10 5 Dispersity Index 2.1 2.1 2.3 4.6 4.9 4.5 Wt. % Acrylic Acid 10 6 2 10 6 2 7 A sodium alkyl allyl sulfosuccinate manufactured and sold by Diamond Shamrock o> l ro Ol o CO Ol o Ol Ol TABLE IV Examples 17 to 42 EXAMPLE 17 18 19 20 21 22 23 24 % Acrylic Acid in High-Mol.-Wt. Polymer 10 10 2 % Acrylic Acid in Low-Mol.-Wt. Polymer 10 10 Wt. % of Low-Mol.-Wt. Polymer in Blend 50 50 50 50 75 75 25 25 Crosslinking Agent* CX-100 (%) 0.4 0.4 0.4 0.4 0.8 0 0.8 0 Finat Tack* 365.7(P) 77(P) 578(P) 271(P) 443(P) 443(P) 462(P) 154(P) Loop Tack (PE) 170(PS) 77(P) 230(PS) 160(PS) 250(PS) 420(PS) ΙOO(PS) 150(PS) 1 * -> e~ 90° Peel (PE) 190(PS) 38(PS) 290(PS) 200(PS) 270(PS) 270(PS) 77(PS) 190(PS) 90° Peel (SS) 500(IPT) 120(PS) 410(PS) 230(PS) 420(SPS) 650(PS F) 310(IPT) 460(IPT) Shear (0.5 kg) 78** 0.08(C) 0.75(C) 0.18(C) 1.98(C) 0.24(C) 245** 21.9(PF) 1/2" Mandrel (PE) <0.4 Fail 8.0 0.4 0.8-0.8 1.6-1.6 Fail <0.4 (12.7mm, 7 days) (11.2) 1.6-6.4 (11.2) Bleed Resistance Very Very Very at 60°C (1 week) Good Poor Good Good Poor Good Good Good • Loop tack to glass **No slip TABLE IV (continued) Examples 17 to 42 EXAMPLE 25 26 27 28 29 30 31 32 % Acrylic Acid in High-Mol.-Wt. Polymer 10 10 % Acrylic Acid in Low-Mol.-Wt. Polymer 10 10 Wt. % of Low-Mol.-Wt. Polymer in Blend 75 75 50 50 50 75 25" 75 Croβslinking Agent* CX-100 (%) 0.4 0.8 0 0.8 0 0.4 0.4 0.4 Finat Tack* 270(P) 347(P) 193(P) 438(P) 158(P) 616(P) 443(P) 308(P) Loqp Tack (PE) 230(PS) 150(P) 160(PS) 260(PS) 190(P) 270(PS) 38(PS) 190(PS) 90 β Peel (PE) 250(PS) 120(P) 230(PS) 400(PS/F) 220(S) 260(PS) 50-200*** 110(PS) I 90° Peel (SS) 460(IPT) 390(IPT) 580(IPT) 290(P) 280(PS) 620(IPT) 400(IPT) 230(P_>) Shear (500/wk) 26.6(PS) 237** 1.98(C) l.KC/ 1.36(C/ 0.9(C) 240** 0.18(C) P 2 /D P 3 /!) 1/2" Mandrel (PE) <0.4 Fail <0.4 8.0-9.6 8.0-9.6 0.4 6.4-1.6 Fail (12.7mm, 7 days) (11.2) 8.0-3.2 9.6-9.6 4.8-4.8 (11.2) Bleed Resistance Very Very Very Very Very at 60°C (1 week) Good Good Good Good Good Good Good Poor ***Slip stick TABLE IV (continued) EXAMPLE 33 34 35 36 37 % Acrylic Acid in High-Mol.-Wt. Polymer 10 10 % Acrylic Acid in __.w-Mol.-Wt. Polymer wt. % of Low-Mol.-Wt. Polymer in Blend 25 5U 75 25 75 Crosslinking Agent* CX-100 (%) 0.4 0.4 0.4 0.4 0.4 Finat Tack* 520(P) 347(P) 385(P) 115(P)*** 350(P) Loop Tack (PE) 100(PS) 160(P_J) 290(P) 40(PS) 220(PS) 90 β Peel (PE) 130(PS) 200(P) 250(PS) 35-120*** 200(F/P) 90 β Iteel (SS) 390(IPT) 540(IPT) 480(SPS) 380(IPT) 210(F/P) Shear (500/wk) 142** 1/2" Mandrel (PE) Fail <0.4 0.8-0.8 Fail 1.6-3.2 (12.7mra, 7 days) (11.2) 0.4-O.4 6.4-4.8 (11.2) Bleed Resistance Very Very at 60 β C (1 week) Good Good Good Good Poor *Locρ tack to glass **No slip ***Sliρ stick TABLE IV (continued) Ξxaπples 17 to 42 EXAMPLE 38 39 40 41 42 % Acrylic Acid in High-Mol.-Wt. Polymer 2 % Acrylic Acid in Lσw-Mol.-Wt. Polymer 6 10 10 Wt. % of Low-Mol.-Wt. Polymer in Blend 25 50 50 50 50 Crosslinking Agent* CX-100 (%) 0.4 0.8 0 0.8 0 Finat Tack* 17.5(P) 446(P) 269(P) 366(P) 192(P) Loop Tack (PE) 140(PS) 140 (PS) 210(PS) 120(PS) 230(PS) 90" Peel (PE) 120 (P) 53-200*** 240(PS) 120(PS) 180(PS ) 90° Peel (SS) 190(P) 460(IPT) 460(IPT) 330(F) 480(P) Shear (500/wk) !.73(C/P) 18.9(P/C) 4.79(C) 7.5(PS) 4.74(C) 19.3(PS) 1/2" Mandrel (PE) 8.0-0.8 Fail 0.8-0.8 Fail 0.8-0.8 (12.7mm, 7 days) (11.2) (11.2) Bleed Resistance Very Very Very at 60°C (1 week) Good Good Good Poor Good *Locp tack to glass **No slip ***Slip stick Example 43 An adhesive formulation showing good alkali remova¬ bility for use in recycle labeling of beverage containers, was formulated from 25 parts by weight of a high-molecu¬ lar-weight polymer containing about 96 percent by weight ethyl acrylate and 4 percent by weight acrylic acid and having a molecular weight of about 400,000; and 75 percent by weight of a low-molecular-weight polymer containing 88 percent by weight ethyl acrylate and 12 percent by weight acrylic acid and having a molecular weight of less than about 12,000. A particular utility of the adhesive is to label recyclable beer kegs where the label is removed by caustic on recycle for refilling.

Claims: WHAT IS CLAIMED IS: 1. A pressure-sensitive adhesive composition comprising in combination, a high-molecular-weight alkyl acrylate polymer having a molecular-weight greater than 10 times the entanglement molecular-weight of the polymer and containing at least about 70 percent by weight of an alkyl acrylate having from 2 to about 4 carbon atoms on the alkyl side chain, and from about 40 percent by weight to about 80 percent by weight of a low-molecular-weight alkyl acrylate polymer, based on the total weight of said high-molecular-weight alkyl acrylate polymer and said low-molecular-weight alkyl acrylate polymer, said low-molecular-weight alkyl acrylate polymer being formed of an alkyl acrylate identical to the alkyl acrylate of said high-molecular-weight alkyl acrylate polymer, having a molecular weight less than 2 times the entanglement molecular-weight of the polymer, and containing at least 70 percent by weight of the alkyl acrylate, the comonomer contents of said high-molecular-weight alkyl acrylate polymer and said low-molecular-weight alkyl acrylate polymer differing by no more than about 10 percent by weight. 2. A pressure-sensitive adhesive composition as claimed in claim 1 in which the high-molecular-weight alkyl acrylate polymer contains at least 90 percent by weight alkyl acrylate. 3. A pressure-sensitive adhesive composition as claimed in claim 1 in which the low-molecular-weight alkyl acrylate polymer contains at least 80 percent by weight alkyl acrylate. 4. A pressure-sensitive-adhesive composition as claimed in claim 2 in which the low-molecular-weight alkyl acrylate polymer contains at least 90 percent by weight alkyl acrylate. 5. A pressure-sensitive-adhesive composition as claimed in claim 1 in which the alkyl acrylate is ethyl acrylate. 6. A pressure-sensitive-adhesive composition as claimed in claim 1 in which the alkyl acrylate is copolymerized with an unsaturated carboxylic acid. 7. A pressure-sensitive-adhesive composition as claimed in claim 6 in which the carboxylic acid is 'acrylic acid. 8. A pressure-sensitive-adhesive composition as claimed in claim 2 in which the alkyl acrylate is copolymerized with acrylic acid. 9. A pressure-sensitive-adhesive composition as claimed in claim 3 in which the alkyl acrylate is copolymerized with acrylic acid. 10. A pressure-sensitive-adhesive composition as claimed in claim 4 in which the alkyl acrylate is copolymerized with acrylic acid. 11. A pressure-sensitive-adhesive composition as claimed in claim 5 in which the ethyl acrylate is copolymerized with acrylic acid. 12. A pressure-sensitive-adhesive composition comprising a high-molecular weight alkyl acrylate polymer comprised of at least 70 percent by weight ethyl acrylate, said high-molecular-weight alkyl acrylate polymer having a molecular-weight which is at least 10 times the entanglement molecular-weight, and a low-molecular-weight alkyl acrylate polymer having a molecular-weight of less than 2 times the entanglement molecular-weight and containing at least 70 percent by weight ethyl acrylate, the balance of said low-molecular-weight alkyl acrylate being present in a concentration of from about 40 to about 80 percent by weight, based on the total weights of the high-molecular-weight alkyl acrylate polymer and the low-molecular-weight alkyl acrylate polymer, and providing a composition having a glass-transition temperature of at least about 40°C below use temperature, said high- molecular-weight alkyl acrylate polymer and/or said low-molecular-weight alkyl acrylate polymer containing an interpolymer amount of at least one unsaturated carboxylic acid. 13. A pressure-sensitive-adhesive composition as claimed in claim 12 in which the carboxylic acid is acrylic acid. 14. An alkali-removable pressure-sensitive adhesive composition comprising a high-molecular-weight copolymer of ethyl acrylate and acrylic acid, said high-molecular-weight copolymer containing about 96 percent by weight ethyl acrylate and about 4 percent by weight acrylic acid and having a molecular-weight greater than 10 times the entanglement molecular-weight, in combination with a low-molecular-weight copolymer of ethyl acrylate and acrylic acid containing about 88 Claim 14, continued. . . percent by weight ethyl acrylate and about 12 percent by weight acrylic acid, said low-molecular-weight copolymer having a. molecular-weight of less than 2 times the entanglement molecular-weight, said pressure-sensitive- adhesive composition having a glass-transition temperature of at least 40 β C below the use temperature thereof.

Inventors: LIN KENNETH SHOU-CHEIN, LIN, KENNETH, SHOU-CHEIN
Applicants: AVERY INTERNATIONAL CORP, AVERY INTERNATIONAL CORPORATION
Application year: 1986
Main classification: C08L33
IPC codes: C08L33, C09J133