JPS6328114B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is composed of a copolymer of polyvinyl lactam, an acrylic ester or a methacrylic ester or a mixture of esters (1), and an ethylenically unsaturated acid (2), and has unique properties combining various properties and characteristics. The present invention relates to compositions useful as pressure sensitive adhesives, which are admixtures in which the pressure sensitive adhesives are used. Pressure-sensitive adhesive compositions are generally applied to a flexible backing or tape in the form of a solution or dispersion in a suitable vehicle such as an organic solvent or water, or in the form of a hot melt without a vehicle. These backing materials or tapes are used to maintain the material during use. For a pressure sensitive adhesive composition to be effective, it must not only have sufficient viscosity, but also sufficient tack and a desired degree of adhesion. All of these properties are generally interdependent, such that a change in one property causes a related change in the other properties. It has long been known that homopolymers of various low molecular weight alkyl acrylic esters are viscous materials that can be used as pressure-sensitive adhesives, particularly tapes or backings for adhesion to the skin. Since it does not have sufficient tack as a spread-on type pressure sensitive adhesive, other selected monomers may be copolymerized with it, as described, for example, in U.S. Pat. No. 3,299,010 to Samour. It was necessary to obtain the desired combined properties. Also, as in the case of a blend of two different water-insoluble hydrophobic copolymers described in Guerin et al., U.S. Pat. It has long been the practice to produce pressure sensitive adhesive compositions by blending compatible components, one or more of which, when combined, can meet the requirements. Additionally, as described in Stoner et al., U.S. Pat. It has also been proposed to form effective, water-insoluble compositions. As pointed out by Stoner et al. in column 4, lines 56-73 of this specification, the reaction products described in this patent are substantially It always has the same properties and always contains the two types of polymer components in the same proportion.
On the other hand, the compositions of the present invention vary in their proportions and properties depending on the proportions of the starting materials. No. 3,975,570 to Ono et al. improves the moisture permeability of conventional pressure sensitive adhesives, which are copolymers of alkyl acrylates and acrylic or methacrylic acids, by blending the copolymer with hydroxyethyl cellulose. It is further stated that blends of such adhesives with poly(vinylpyrrolidone) do not show improved water permeability. This time, water-soluble poly(N-vinyl lactam) and
The following structural formula: (In the formula, R' represents hydrogen or a methyl group,
R ₁ represents an alkyl group having 1 to 14 carbon atoms) or a mixture of esters;
By creating an optically transparent mixture consisting of a water-insoluble copolymer with a carboxylic acid group-containing ethylene monomer (B) in an amount of 1 to 12%, preferably 4 to 7% by weight of the copolymer. It is now possible to produce water-insoluble pressure sensitive adhesive compositions that have excellent viscosity, tack and adhesion and can be applied to backings using conventional hot melt application equipment. It's been found. One of the components, a copolymer, is viscous, with a glass transition temperature below 0°C and 350°C.
It has a viscosity of less than 50,000 cps at (176.7°C) and is soluble in organic solvents (i.e., substantially free of crosslinks) and is therefore not sufficient on its own to be useful as a pressure-sensitive adhesive. It has sufficient adhesive strength. The N-vinyl lactam used as a polymer in the present invention has the following structural formula: (wherein X represents an alkylene bridge having 3 to 5 carbon atoms), such as 1-vinyl-2-pyrrolidone, 1-vinyl-5-methyl-2-pyrrolidone,
1-vinyl-2-piperidone and N-vinyl-
ε - A lactam, such as caprolactam,
The polymer can have a molecular weight from 10,000 to over 1,000,000, with polymers of 1-vinyl-2-pyrrolidone being particularly preferred. The amount of N-vinyl lactam polymer in the blend can vary from 1 to 30% by weight of the blend, depending on the copolymer present and the desired properties of the blend. Also, the amount of copolymer present in the blend is
The pressure-sensitive adhesive composition may contain conventional additives, such as stabilizers, to prevent degradation of the admixture during processing at elevated temperatures, which can vary from 70 to 99% by weight of the admixture. Although small amounts of additives may be included, it is desirable to contain only blends of N-vinyl lactam polymers and certain copolymers. In addition to stabilizers, customary additives such as pigments, colorants, etc. may also be present. Ethylene-based monomers containing acid groups that can be copolymerized with esters include carboxylic acid groups or It can contain a sulfonic acid group or a phosphoric acid group, but
The acid group in the ethylene monomer is preferably a carboxylic acid, and acrylic acid is particularly preferred as the monomer. Esters of the ethylenically unsaturated monomers with which the acid can be copolymerized are, for example, butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate and the corresponding methacrylates or mixtures of these esters, having from 1 to 14 carbon atoms. Esters of mixtures of various alcohols with acrylic acid are preferred;
Particularly preferred are alkyl acrylates in which the alkyl group has 4 to 8 carbon atoms. The copolymer need not consist exclusively of a particular ester monomer and an ethylenically unsaturated monomer containing acid groups, but may also include other copolymerizable ethylenically unsaturated monomers, such as vinyl acetate, styrene or acrylonitrile. 20% by weight of total copolymer
It can contain up to Generally, the presence of such a third comonomer in the copolymer does not adversely affect the properties of the pressure sensitive adhesive, and in some cases may reduce cost or increase adhesion. Sometimes it is advantageous to do so. Miscible by mixing the respective solutions or dispersions of the N-vinyl lactam polymer and copolymer in any vehicle or solvent that are miscible with each other and then removing the vehicle or solvent, such as by evaporation. can manufacture things, but
It is also possible to blend the polymers or copolymers using conventional mixing equipment such as a two roll mill or sigma plate mixer. The amount of N-vinyl lactam polymer contained within the specified proportion range, i.e. 10 to 30% by weight of the mixture
In the case of admixtures where the amount is close to the upper limit of
Pressure-sensitive adhesive compositions exhibit increased water vapor permeability compared to compositions containing small amounts of polymers, which may be useful for adhesive tapes or adhesives with porous backings or reinforcements intended for application to the skin. In the case of sheets, this is an advantageous feature. When different polymers and copolymers are mixed, they are usually considered to be incompatible with each other, and 1
Although it is not conceivable that a homogeneous admixture with properties different from that of the other component could be formed, the admixture of the present invention is optically clear, at best only slightly hazy in appearance, and at least This shows that the mixture is homogeneous to the extent that particles of both components with diameters larger than 4000 Å are not separated. Due to this homogeneity, the low adhesion of the viscous copolymer is increased and the high fluidity is reduced by the fact that an N-vinyl lactam polymer can be present in the blend, which acts as a toughening agent. The admixture according to the invention can be applied to an adhesive sheet by spreading, painting or pouring a mixed solution or dispersion of the admixture onto a backing and then removing the solvent or liquid vehicle, e.g. by evaporation. or to flexible backings or reinforcements commonly used in the manufacture of adhesive tapes; the viscosity of the hot melt of this admixture is less than 100,000 centipoises at 350°C (176.7°C); The articles have the unique possibility of being applied in the melt using conventional hot melt application equipment; also, no curing or crosslinking of the admixture is necessary. Conventional pressure-sensitive adhesives containing copolymers of alkyl acrylate and acrylic acid or methacrylic acid have sufficiently high viscosity and appropriate adhesive strength, but they melt at a temperature of 100,000 centipoises or more at 350 °C (176.7 °C). Due to its viscosity, it cannot be applied to the backing in the molten state using conventional equipment. In order to maximize the safety and service life of the admixture, in addition to the N-vinyl lactam polymer and copolymer, it is necessary to include, for example, tetrakis-[2,4-di-tert-butyl] in the pressure-sensitive adhesive composition. It is advisable to add a small amount of a customary stabilizer, such as 1% by weight of -phenyl]-4,4'-biphenylylene diphosphonite. The essence of the present invention will now be more fully explained by some examples, but these examples are not intended to limit the scope of the invention. The molecular weights used in the examples are the maximum molecular weights determined by gel permeation chromatography. Examples 1-15 A series of copolymers of alkyl acrylates and various proportions of acrylic acid are prepared by dissolving the desired proportions of monomers in a suitable solvent such as benzene or ethyl acetate, for example 2-tert-butylazo-
It was made by conventional solution polymerization methods using a small amount (0.1% by weight of monomer) of a free radical generator such as 2-cyanopropane as a polymerization initiator. The polymerization reaction is carried out at a temperature of 85-95°C until a high degree of conversion on the order of 97% occurs, producing a copolymer with a molecular weight of 62,000 to 566,000, which in itself is a pressure-sensitive adhesive. The adhesive strength is insufficient. When these copolymers were heated in vacuum to remove the solvent, they rapidly became viscous, but did not have sufficient tack on their own to be a satisfactory pressure sensitive adhesive. The relationship between these copolymers and molecular weight is shown in the following table:

Table: A series of 1-vinyl-2-pyrrolidone homopolymers, all water-soluble but reported to have different molecular weights, were obtained from commercial sources as follows: Example No.
Polyvinylpyrrolidone (molecular weight, in thousands) (1) 10 (2) 40 (3) 360 Blends of the two aforementioned series in various weight ratios were prepared as shown in Table 1. In some cases, the acrylic ester copolymer still dissolved in the polymerization solvent is mixed with a solution of poly(vinylpyrrolidone) dissolved in a compatible solvent, such as chloroform, and then distilled under reduced pressure. The solvent was removed from both by. In other cases, the solvent is first removed from the solution of the acrylic ester copolymer by heating under reduced pressure, and then this solvent-free copolymer is passed through a heated two-roll mill. Therefore, it is blended with solvent-free poly(vinylpyrrolidone). The admixture is then applied to a standard backing or support consisting of 1.5 mm polyethylene terephthalate film (Mylar), by spreading the admixture solution in solution onto the film. This is done by spreading and then removing the solvent by evaporation or applying by calendering the mixture produced by milling. The product in each case was a pressure-sensitive adhesive tape with an adhesive layer 1 to 3 mm thick. The adhesion of this tape was then measured with the results listed in the following table. Sample viscosity was measured using a Polyken sample viscosity tester as described in U.S. Pat. No. 3,214,971, which has four functional parts; Spring Inc., Newsletter 750/FG, 1961
A steel test tube 1 attached to a compression load spring (revised in February 2016) is brought into contact with a ring 3 having an opening slightly larger than the test tube diameter, and the ring is moved downward, and then a ring carrier 4 that moves upward to remove the ring; this carrier has a diameter of 0.1 inch (0.254
cm)/second. At the beginning of the test,
The carrier is at the top of its travel, and the ring rests on the carrier in line with the test tube below. To perform the test, place a piece of tape over the ring, adhere the sides, and begin the test while the ring is under tension. As the carrier is driven downward by a constant speed motor, the adhesive surface exposed through the opening in the ring comes into contact with the flat surface of the test tube, and as the carrier continues to descend further downward, the adhesive surface exposed through the ring opening comes into contact with the tape. The ring attached to the test tube will be suspended above the test tube. The direction of the carrier's movement is then reversed and the ring is pulled back up, thereby separating the tape from the test tube surface. Separation should begin after 1 second of contact between the test tube and adhesive. The force required to pull the tape away from the test tube is recorded on the gauge. This recorded value is the viscosity value of the sample. Measurements were made using a load of 100 grams/cm ² . In addition, the peel adhesion value is 1 inch wide adhesive tape on stainless steel at a temperature of approximately 75㎓ (23.9℃).
It represents the force required to separate from a steel surface after 2 minutes of adhesion. The tape is removed from the surface at a rate of 12 inches (30.5 cm) per minute at a 180 degree angle. Creep resistance value is 104〓±2〓 (40℃±1.1℃)
Measurements are made by mounting a polished stainless steel tube with an outer diameter of 1 inch held horizontally in a constant temperature room maintained at a temperature of . The steel tube has a tube extending along the top surface parallel to the axis of the tube. 1/
A 16 (0.159 cm) wide slot is provided and a 6 inch (15.24 cm) length of the adhesive tape to be tested is placed over the steel tube with the adhesive side in contact with the tube and its free ends are placed on either side of the tube. Make sure they hang approximately the same length so that the tape hangs vertically across the slot. Each length of tape is no more than 1 inch (2.54 cm) wide, and a weight of 1 pound (454 grams) per inch (2.54 cm) of tape width is secured to the lower end of each length. After holding the weighted tape in a thermostatic chamber for 15 minutes, pull the tape across the gap in the slot and measure the time it takes for each end to descend by 1/2 inch. This creep resistance value is expressed in time. Melt viscosity at 350° (176.7°C) was determined using a Brookfield Thermosel (viscosity meter model RVT) using a No. SC4-27 spindle at 2.5 revolutions per minute.
Measured as viscosity. These results were shown in the following table:

【table】

[Table] High percentage of PVP (poly(vinylpyrrolidone))
Compositions comprising blends of alkyl acrylate copolymers containing Water vapor permeability is a desirable property, especially in sanitary adhesive tape products for application to the skin. The water vapor permeability was determined by ASTM E96 Method E.

The blends in each example are optically clear blends and, as is clear from the foregoing, all blends are capable of forming effective pressure sensitive adhesive tapes. From the table above, what effect occurs with changes in the amount of acrylic acid present in the copolymer, the molecular weight of the copolymer, the relative proportion of the copolymer to poly(vinylpyrrolidone), and the molecular weight of the poly(vinylpyrrolidone). It is also obvious. Properties of other admixtures of the present invention can also be easily determined by extrapolation or interpolation from the foregoing results, but generally when sulfonic acid or phosphoric acid groups are present, the It should be remembered that less amount of acid comonomer is required to achieve the same effect. The same results can be obtained with copolymers of acrylic acid and other alkyl acrylates or mixtures thereof, and with other water-soluble polyvinyl lactams in place of poly(vinylpyrrolidone). can be obtained.

Claims (1)

[Claims] 1 The following structural formula: (In the formula, X represents an alkylene bridge having 3 to 5 carbon atoms.) Water-soluble vinyl lactam polymer (1)
and the following structural formula: (In the formula, R' represents hydrogen or a methyl group,
(R ₁ represents an alkyl group having 1 to 14 carbon atoms) and 1 to 12% by weight of the acid group-containing ethylene monomer (B) of the ester or mixture of esters (A) and the copolymer (2). and a water-insoluble viscous copolymer (2), wherein said polymer (1) is present in an amount of 1 to 30% by weight of the blend; Copolymer(2)
is present in an amount of 70-99% by weight of the admixture, and 0
It has a glass transition temperature below 350°C, has virtually no crosslinking, and has a
1. A pressure-sensitive adhesive composition having a viscosity lower than that of centipoise and having insufficient adhesive strength as a pressure-sensitive adhesive by itself. 2. The composition according to claim 1, wherein X represents _-CH2 - _CH2 - _CH2- . 3. Composition according to claim 1 or 2, characterized in that R' represents hydrogen. 4. Composition according to any one of claims 1 to 3, characterized in that _R1 is an alkyl group having 4 to 8 carbon atoms. 5 R ₁ is an n-butyl group,
A composition according to claim 4. 6. The composition according to claim 4, wherein R ₁ is a 2-ethylhexyl group. 7. The composition according to any one of the preceding claims, characterized in that the monomer (B) contains a carboxyl group. 8. Composition according to any one of the preceding claims, characterized in that monomer (B) is acrylic acid. 9. Claim 2, characterized in that the amount of water-soluble polymer (1) is from 1 to 8% by weight of the mixture.
The composition according to any one of Items 1 to 8.