NL8001258A - PRESSURE SENSITIVE ADHESIVE. - Google Patents

Description

*. * «• d VO 179

Pressure sensitive adhesive.

The invention relates to a composition which can be used as a pressure-sensitive adhesive, which composition consists of a mixture of a polyvinyl lactam and a copolymer of 1] an acrylic or methacrylic ester or a mixture of esters, 5 and 23. ethylenically unsaturated acid, which mixture has a unique combination of properties.

Pressure sensitive adhesive compositions are usually applied to a flexible support or tape, on which they are supported during use by being in the form of a solution or dispersion in a suitable carrier such as an organic solvent or water, or in the form of a hot melt without coating as a carrier. In order to be useful, pressure sensitive adhesive compositions must have not only good adhesion, but also good cohesive strength and the desired high degree of adhesion. All of these traits are usually related, with a change from one trait usually causing a change in the other. While various low molecular weight homopolymers of alkyl acrylates have long been known as tacky materials, they do not have cohesive strength enough to be used per se as a pressure sensitive adhesive, for all those used on walls or supports intended for adhering to the skin , and it has therefore been necessary to copolymerize them with selected other monomers in order to achieve the desired combination of properties, see eg United States Patent 3,299,010.

It has also long been common practice to prepare pressure sensitive adhesive compositions by mixing together compatible components, each of which lacks one or more of the required properties but satisfies the requirements in combination, e.g. in the case of blends of two different hydrophobic, 800 1 2 58 * ψ - 2 - insoluble copolymers, as described in U.S. Pat. No. 4,045,517.

It has also already been proposed to react water-soluble poly (N-vinyl-lactam compounds) with polymeric carboxylic acids (including copolymers) to form water-insoluble compositions that can be used for various purposes, see U.S. Patent 2,901,457. As indicated in column 4, lines 56-73, the reaction product described always has almost the same properties and contains the two polymeric components in the same proportions regardless of the ratios in which the two were used to prepare the product. The compositions of the invention, on the other hand, vary in properties and proportions of the components depending on the proportions of the starting materials.

U.S. Pat. No. 3,975,570 proposes to improve the water vapor permeability of known pressure sensitive adhesives that are copolymers of alkyl acrylates with acrylic or methacrylic acid by mixing them with hydroxyethyl-20 cellulose. Mixtures of such adhesives with poly (vinylpyrrolidone) are not indicated to provide improved water vapor permeability.

It has now been found that water-insoluble pressure sensitive adhesive compositions with excellent tack, cohesion and adhesion and the ability to be supported on a known hot melt coating equipment can be obtained by an optically clear mixture to prepare a water-soluble poly (N-vinyl lactam) and a water-insoluble copolymer of A3 an ester or mixture of esters of formula 1 of the formula sheet wherein R 1 is hydrogen or me

represents thyl, and represents alkyl of 1 to 14 carbon atoms, and B) comprises from 1 to 12% by weight, preferably 4 to 7% by weight, of a copolymer of an acid group-containing ethylene monomer, which copolymer is tacky, with has a glass transition temperature below 35 ° C, and a viscosity of less than 50,000 cp at 176.7 ° C

800 1 2 58 4Τ 1 - 3 - and is soluble in organic solvents (i.e., has virtually no cross-links), so that in itself it has insufficient cohesive strength to be used as a pressure sensitive adhesive.

The N-vinyl lactam compounds, the polymers of which can be used according to the invention, include the compounds of formula 2, wherein X represents an alkylene bridge with 3-5 carbon atoms, e.g. 1-vinyl-2-pyrrolidone, 1-vinyl-5-methyl-2-pyrrolidone, 1-vinyl-2-piperidone, and N-vinyl-1-caprolactam; the polymers can have molecular weights from 10,000 to 1,000,000 or more.

Polymers of 1-vinyl-2-pyrrolidone are preferred. The amount of polymeric N-vinyl lactam in the mixture can vary from 1 to 30% by weight of the mixture, depending on the copolymer present and the properties desired in the mixture.

The amount of copolymer present in the mixture can vary from 70 to 99% by weight of the mixture. Preferably, the pressure sensitive adhesive composition contains only the mixture of polymeric N-vinyl lactam and the specified copolymer, although small amounts of conventional additives such as stabilizers may also be present to prevent deterioration of the mixture during processing at elevated temperatures. Other conventional additives such as pigments, colorants and the like may also be present.

The ethylenic monomer containing an acid group and copolymerizable with the ester may contain a carboxylic acid group or sulfonic acid group or phosphonic acid group, e.g. acrylic or methacrylic acid, crotonic acid, maleic acid, 2-sulfoethyl methacrylate, and 1-phenylvinyl phosphonic acid. The acid group in the ethylene monomer is preferably an carboxylic acid group, most preferably acrylic acid. The ester with which the ethylenically unsaturated monomeric acid is copolymerized, e.g. butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate as well as the corresponding methacrylates or mixtures thereof. Esters of acrylic acid with mixtures of different alcohols with 1-14 carbon atoms are preferred; Most preferred are alkyl acrylates in which the alkyl contains 800-1 2 58 -4-4 groups 4-8 Carbon atoms. The copolymer need not consist solely of the specified ester monomer and an acid group-containing ethylenic monomer, but may contain up to 20% by weight, based on the total copolymer, of another copolymerizable ethylenically unsaturated monomer, e.g. vinyl acetate, styrene or acrylonitrile. In general, the presence of such a third comonomer in the copolymer does not adversely affect the properties of the pressure sensitive adhesive and may sometimes be desirable in connection with reduction of the cost or increase of the cohesive strength.

The mixture Can be prepared by mixing solutions or dispersions of the polymeric N-vinyl lactam and the copolymer in any desired carriers or solvents that are miscible with each other, then the carrier or the solvent e.g. by removing evaporation. It is also possible to mix the polymer or copolymer with a known mixing equipment, e.g. a two-roll mill or sigma blade mixer.

In the case of blends containing amounts of polymeric N-vinyl lactam near the upper end of the specified ratio range, ie, 10-30 wt.% Relative to the blend, the pressure sensitive adhesive composition exhibits an increased water vapor permeability compared to compositions containing lesser amounts of polymer. This is an advantage in the case of adhesive tapes or sheets with a porous support or reinforcement, which are intended to be applied to the skin.

While various polymers and copolymers are usually considered incompatible with each other when mixed, and are not considered capable of forming a homogeneous blend with properties other than all of the components, the blends of the invention are optically clear or have are only slightly hazy in appearance, demonstrating that the mixtures are at least homogeneous such that no discrete particles of any component other than those having diameters in excess of 400 nm are present. Because of this homogeneity, 800 becomes 1 2 58

J

- Increased the low cohesive strength of the tacky copolymer and decreased the high fluidity due to the presence in the polymeric N-vinyl lactam mixture serving as the reinforcing agent.

The compositions of the invention may be applied to any conventional flexible supports or reinforcements used in the manufacture of adhesive tapes and sheets by spreading, coating, or pouring a mixed solution or dispersion of the mixture onto the substrate. support, then the solvent or liquid carrier, e.g. by removing evaporation; however, the blends have the unique ability to be applied in the molten state using conventional hot melt coating equipment, because the viscosities of their hot melt are less than 100,000 cps at 176.7 ° C; no curing or cross-linking of the mixture is required. Known pressure sensitive adhesives, which contain copolymers of alkyl acrylates and acrylic or methacrylic acid of sufficiently high viscosity to have adequate cohesive strength, have a melt viscosity above 100,000 cps at 176.7 ° C and cannot melted condition on a support with conventional equipment.

In order to realize maximum stability and life of the mixture, it may be desirable to include a small amount of a conventional stabilizer in the pressure sensitive adhesive composition in addition to the polymeric N-vinyl lactam and the copolymer, e.g. 1 wt% of tetrakis / T2.4-di-tert-butyl-phenyl-7-4.4'-biphenylylene diphosphonite.

The invention is further illustrated by the examples. The molecular weights reported herein are the peak 30 molecular weights determined by gel permeation chromatography.

Examples I-XV

A series of copolymers of alkyl acrylates with different amounts of acrylic acid were prepared according to conventional solution polymerization procedures by dissolving the desired amounts of monomers 800 1 2 58 r-6 - in a suitable solvent, e.g. benzene or ethyl acetate, and as a polymerization initiator a small amount (0.1% by weight of the monomers) of a free radical source, e.g. benzoyl peroxide or 2-tert-butylazo-2-cyanopropane.

Polymerization was carried out at 85-95 ° C until a high degree of conversion of the order of 97% was achieved, in order to obtain copolymers with insufficient cohesive strength to be used per se as pressure sensitive adhesives, which molecular weights of 62,000 to 566,000 owned. These copolymers, after removal of the solvent by heating under reduced pressure, became aggressive tacky in nature but lacked cohesive strength to be satisfactory pressure sensitive adhesives per se. The copolymers and their molecular weights are indicated below.

15 No. Acrylic ester weight ratio by weight in acrylic ester thousands to acid (1) n-butyl 98: 2 82 (23 "97: 3 127 20 (33" 97: 3 200 (43.95! 5 58 (53 2-ethylhexyl 98) : 2 566 (63 "97: 3 128 (73 * 97! 3 207 25 (83 - 96.5: 3.5 304 (93" 96: 4 62 (103 * 96: 4 84 (113 ”96: 4 112) (123 - 95.3 ί 4.7 105 30 (133 "94.5: 5.5 85 (143 ·" 94.5: 5.5 105 (153 ”93: 7 105

A range of 1-vinyl-2-pyrrolidone homopolymers, all water soluble but of different molecular weights, 35 and commercially available, were as follows: 800 1 2 58 - 7 -

No. Polyvinylpyrrolidone molecular weight in thousands

Cl) 10 C2) 40 5 (3) 360

Then, mixtures of the above two series in different weight ratios were prepared, as indicated in Table A. In some instances, the acrylate copolymer, still dissolved in the solvent in which it was polymerized, was mixed with a solution of the poly (vinyl pyrrolidone) in a compatible solvent such as chloroform, and then the two solvents were removed by evaporation under reduced pressure.

In other cases, the solvent of the acrylate copolymer solution was first removed by heating under reduced pressure, and then the solvent-free copolymer was mixed with solvent-free polyvinylpyrrolidone) by grinding with a heated two-roll mill. The mixture was then applied to a standard support or support, which consisted of a 38ym polyethylene terephthalate film (Mylar), the mixtures formed in solution were applied by spreading the solution over the film before the solvent was evaporated and the millings formed by calendering.

In all cases, the product was a pressure sensitive adhesive tape with an adhesive layer having a thickness of 25-76 µm.

The adhesive properties of the tape were then determined. They are shown in the table. The probe adhesive strength was determined using a Polyken probe adhesive investigator, described in U.S. Pat. No. 3,214,971 with the following four functional parts: 1) a cylindrical steel probe, connected to the compression-loaded spring of 2) a series l Hunter mechanical force gauge (Hunter Spring Company, Brochure 750 / FG, revised February 1961), 3) a ring with a slightly larger opening than the diameter of the 35 probe, and 800 1 2 58 - 8 - 4) a carrier for the ring, which moves down to wrap the ring around the probe and then moves up to remove the ring.

The carrier moves at a rate of 0.254 cm / sec. At the start of the test, the support is at its top point and the ring rests on the support such that the opening in the ring is aligned with the probe below. When performing the test, a strip of the tape is placed with the adhesive down over the ring such that the opening 10 in the ring is spanned. When the carrier is moved downward by a synchronous motor, the surface of the adhesive released through the opening is brought into contact with the smooth surface of the probe so that the tape and the associated ring are suspended on the probe as the carrier continues is moved down. Then, the direction of movement of the wearer reverses to pick up the ring again, separating the band from the surface of the probe. The separation begins after 1 second contact between the probe and the adhesive. The force required to separate the tape from the probe is determined by one meter. The determined value is the probe adhesive force value. The measurements were made with a load 2 of 100 g / cm.

The peel-off adhesion values represent the forces required to remove 2.5 cm wide adhesive tape from a stainless steel surface after contacting each other for 2 minutes at a temperature of about 23.9 ° C. stood.

The tape is pulled from the surface at an angle of 180 ° at a speed of 30.5 cm / minute.

The creep resistance values are determined by providing a polished stainless steel tube with an external diameter of 2.5 cm, which is placed horizontally in a chamber with a constant temperature of 40 ° C + _ 1.1 ° C, with a 0.159 cm wide slot parallel to the axis of the pipe over its top side. A 15.24 cm length of adhesive tape to be examined is placed over the tube 35 with the adhesive surface in contact with the tube while the free ends are approximately the same distance on opposite sides of the tube towards hang down and the strap is positioned over the slot in a direction perpendicular to the slot EACH piece of strap is no more than 2.54 cm wide and at each of the under-5 ends weighing 454 g per width of the 2.54 cm band attached After the loaded band was held in the chamber for 15 minutes, it was cut transversely along the opening in the slot and the time was measured in hours, which each end needed to pass over a distance of 1.27 cm downwards The creep resistance was expressed in hours.

The melt viscosity at 176.7 ° C was measured as Brookfield Thermosel (Viscometer Model RVT) viscosity with a number SC4-27 coil at 2.5 rpm.

The results are shown in Table A.

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Certain compositions of blends of alkyl acrylate copolymers containing higher levels of PVP had a water permeability (Table B) of twice or more that of the known unmixed acrylate pressure sensitive adhesives. Water permeability of an adhesive is a desirable property, especially for health care adhesive tapes for application to the skin.

It is measured according to ASTM E96 procedure E.

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The blend in each of the examples was an optically clear blend, and all blends, as can be seen from the foregoing, formed useful pressure sensitive adhesive tapes. It is also clear from the preceding tables what consequences are obtained by variations in the amount of acrylic acid present in the copolymer, the molecular weight of the copolymer, the relative ratios of the copolymer to polyvinylpyrrolidone, and the molecular weight of the polyvinylpyrrolidone). The properties of other mixtures according to the invention can be easily obtained by extrapolation or interpolation of the above-mentioned results, bearing in mind that generally less acidic comonomer is required when a sulfonic or phosphonic acid group is present, to achieve the same effect as when a carboxylic acid group is used.

Similar results can be obtained using acrylic acid copolymers with other alkyl acrylates or mixtures thereof and by using other water-soluble polyvinyl lactam compounds instead of polyvinylpyrrolidone).

Λ 800 1 2 58

Claims (10)

A composition, characterized in that it comprises an optically clear mixture of 13 a water-soluble polymer of a vinyl lactam of formula 1 of the formula sheet, wherein X represents an alkylene bridge of 3-5 carbon atoms, and 2.3 a tacky in water insoluble copolymer, which A3 represents an ester or a mixture of esters of formula 2, wherein R 1 represents hydrogen or methyl, and alkyl of 1 to 14 carbon atoms, and B) 1 to 12% by weight, based on the copolymer 23 of 10 an acid group-containing ethylenic monomer, which polymer 13 is present in an amount of 1-30 wt.% of the mixture, while copolymer 23 is present in an amount of 70-99 wt.% of the mixture, a glass transition temperature has a temperature below 0 ° C, and has virtually no cross-links, and has a viscosity of less than 50,000 cp at 176.7 ° C, so that it alone does not have cohesive strength to be used as a pressure sensitive adhesive. Composition according to claim 1, characterized in that X represents -CH2-CH2-CH2-. Composition according to claim 1 or 2, characterized in that R 'represents hydrogen. Composition according to one or more of claims 1 to 3, characterized in that it represents alkyl of 4-8 carbon atoms. Composition according to claim 4, characterized in that R 25 represents n-butyl. Composition according to claim 4, characterized in that it represents 2-ethylhexyl. Composition according to one or more of claims 1 to 6, characterized in that monomer B3 contains a carboxyl group. Composition according to one or more of claims 1 to 7, characterized in that monomer B3 is acrylic acid. Composition according to one or more of claims 2-8, 800 1 2 58-16 - characterized in that the amount of polymer is 1-8% by weight of the mixture. 10. Adhesive sheet material, comprising a flexible support and a pressure-sensitive adhesive layer thereon, characterized in that it comprises a composition according to one or more of claims 1-9. 80 0 1 2 58 R 'H2C = C-C = 0 0 R1 / fX-s. (t = 0 CH = CH2 The Kendall Company 80 0 1 2 * 8