JPH0255719A - Pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE:To improve thermal aging resistance, weatherability and pressure- sensitive adhesion performance without using any solvent by incorporating a specified hydrogenated liq. polyisoprene contg. hydroxyl groups, a compd. contg. phenol residues and a polyisocyanate compd. together. CONSTITUTION:A hydrogenated liq. polyisoprene (A) contg. hydroxyl groups, having an MW of 700-7,000, a vinyl bond content of 20% or less, a hydroxyl group content per molecule of 1.5 or more and wherein 40% or more of C-C double bonds in the molecular chain are hydrogenated is obtd. by radical- polymerizing an isoprene monomer in the presence of a polymn. catalyst consisting of H2O2, an azo compd. having a hydroxyl group {e.g., 2,2'-azobis[2- methyl-N-(2-hydroxyethyl)propionamide]}, and a peroxide having a hydroxyl group (e.g., cyclohexanone peroxide). 100 pts.wt. component A are compounded with 0.01-5 pts.wt. compd. (B) having 2-4 phenol residues [e.g., 2,2'-methylene-bis(4-methyl-6-tert-butylphenol) and a polyisocyanate compd. (C) wherein the ratio of the hydroxyl group of the component A to the NCO group is 0.5-4 by equivalent (e.g., tolyene diisocyanate).

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a liquid polymer post-crosslinking pressure-sensitive adhesive composition having excellent heat aging resistance and weather resistance.

(Prior Technology) Conventionally, solid dems such as natural rubber have been used as adhesives. In recent years, from the viewpoint of saving resources, saving energy, and improving productivity, attempts have been made to create adhesives by using a low molecular weight liquid polymer and post-crosslinking it with a crosslinking agent. Compared to the method using solid rubber, this method using liquid/IJ rubber is easier than masticating, cutting, and cutting the rubber.
There is no need for processes such as dissolution, and since there is no need to use solvents, there is no need for drying and recovery processes, which saves time and energy, simplifies equipment, and further improves production. It has many advantages such as significantly faster speed. As a method for obtaining an adhesive using this liquid Dem, O
A method using low molecular weight monopolyisoprene with H groups introduced into the side chain (JP-A-57-47368), a method using polybutadiene having hydroxyl groups at both ends (JP-A-62-263275) etc. are known. These methods have fully achieved their objectives in terms of energy saving and productivity improvement, and their performance as adhesives is generally satisfactory. However, the environment in which pressure-sensitive adhesives are used is becoming more severe year by year, and in addition to the above-mentioned properties, more advanced performances such as heat aging resistance and weather resistance are now required. Conventional pressure-sensitive adhesives based on diene rubbers are no longer suitable for this purpose.

(Problems to be Solved by the Invention) An object of the present invention is to obtain a solvent-free adhesive that is excellent in heat aging resistance and weather resistance, and has sufficient adhesive performance, using a liquid polymer as a raw material.

(Means for Solving the Problems) According to the present invention, the above object is achieved by a specific hydroxyl group-containing liquid hydrogenated isoprene or a composition containing the same. That is, the present invention provides (1) a molecular weight of 700 to 7;
000. Vinyl bond amount is 20 or less, 1.0% per molecule.
A hydroxyl group-containing hydrogenated liquid polyurethane having 5 or more hydroxyl groups and hydrogenating 40 or more carbon-carbon double bonds in the molecular chain, (2) 100 weight of the hydroxyl group-containing hydrogenated liquid polyisoprene (3) a compound having 2 to 4 phenol residues in an amount of 0.01 to 5 parts by weight relative to 1 part by weight, and (3) a ratio of hydroxyl groups to NCO groups in the hydroxyl group-containing hydrogenated liquid polyisoprene. The present invention relates to a pressure-sensitive adhesive composition comprising a polyisocyanate compound in an amount of 5 to 4 equivalents.

The vinyl bond amount (1,2 or 3,4 bond amount) of the hydroxyl group-containing liquid Reimprene used in the present invention is 20
% or less. If the amount of vinyl bonds exceeds 20, mechanical properties such as rubber elasticity at low temperatures of the polyurethane deteriorate. The microstructures of 1,4-cis, 1,4-trans, 1,2-vinyl and 3,4-vinyl are based on values determined from 'H-NMR spectra.

Further, the number average molecular weight of the hydroxyl group-containing liquid 1 + physodelene is required to be 700 to 7,000.

When the number average molecular weight is less than 700, the cured product with the polyisocyanate compound does not have good rubber elasticity. Also 7
,000, the polyisoprene will no longer exhibit good fluidity. Hydrogenated polyisoprene obtained by hydrogenating this also does not exhibit fluidity. The number average molecular weight of the polyisoprene is preferably 1,000 to s, o o
It is o.

The number of hydroxyl groups (=average number of hydroxyl groups per molecule) of the hydroxyl group-containing liquid polyisoprene is required to be 1.50 to 4.0. If the number of hydroxyl groups is less than 1,50, sufficient crosslinking cannot be obtained in the reaction with the polyisocyanate compound, resulting in problems such as poor mechanical strength of the polyurethane. When the number of hydroxyl groups exceeds 4.0, the crosslinking density becomes too high and the cured product does not exhibit good rubber elasticity. Therefore, the number of hydroxyl groups must be within the above range, preferably 1.8 to
It is 3.0.

This hydroxyl group may be located either at the end of the molecular chain or within the chain, but those located at both ends are preferably used.

Next, the method for producing the hydroxyl group-containing liquid polyisoprene and its hydrogenated product of the present invention will be described. The hydroxyl group-containing liquid polyisogrene referred to in the present invention is known or can be easily produced by known methods. For example, isoprene monomer can be replaced with hydrogen peroxide, an azo compound having a hydroxyl group (e.g. 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)glopionamide], etc.) or a peroxide having a hydroxyl group (e.g. cyclohexanone peroxide). etc.) as a polymerization initiator to obtain a hydroxyl group-containing liquid polyisoprene.

The amount of the polymerization initiator used is, for example, H2O21,2-12,9.2.2'-azobis-[2-methyl-N-(2-hydroxyethyl)-
Suitable amounts are 9.2 to 92 g of teropionamide) and 7.6 to 76 g of cyclohexanone peroxide. Although polymerization can be carried out without a solvent, it is preferable to use a solvent for ease of controlling the reaction. As the solvent, ethanol, isoglonol, etc. are usually used. Suitable reaction temperature is 100 to 150°C and reaction time is 5 to 15 hours.

Hydroxyl group-containing liquid preisoprene can also be obtained by anionically polymerizing an imprene monomer using a catalyst such as naphthalene dilithium to produce isozolene ring I remer, and further reacting with a monoeix compound or the like. Although polymerization can be carried out without a solvent, it is preferable to use a solvent from the same viewpoint as in the case of radical polymerization. Saturated hydrocarbons such as hexane and cyclohexane are used as the solvent. Reaction temperature is 50-100
℃, and the reaction time is suitably 1 to 10 hours.

In some cases, a liquid polyisoprene having a hydroxyl group introduced into its side chain by an addition reaction may also be used (for example, JP-A-57-16003).

In the present invention, the above-mentioned polyisogrene is used after being hydrogenated. At this time, 40 or more carbon-carbon double bonds in the polyisograin are hydrogenated.

If it is less than 404, there is a problem of deterioration of heat resistance and light resistance due to heat or light due to double bonds of the cured product with the polyisocyanate compound. Preferably, the hydrogenation rate is 60% or more, more preferably 80% or more.

The hydroxyl group-containing hydrogenated liquid polyisoprene used in this invention can be obtained by hydrogenating the hydroxyl group-containing liquid polyisoprene produced as described above by a known method using a homogeneous catalyst, a heterogeneous catalyst, etc.

When using a homogeneous catalyst, a saturated hydrocarbon such as hexane or cyclohexane or an aromatic hydrocarbon such as benzene, toluene or xylene is used as a solvent at a reaction temperature of room temperature to 150°C and under a hydrogen pressure of normal pressure to 50 kg/cm2. A hydrogenation reaction takes place. As a homogeneous catalyst, a Ziegler catalyst made of a combination of a transition metal halide and an alkylated product such as aluminum, an alkaline earth metal, or an alkali metal is used at 0.01 to 0.1 mo1 per double bond of the polymer.
Use about %. The reaction usually completes in 1 to 24 hours.

When using a heterogeneous catalyst, saturated hydrocarbons such as hexane and cyclohexane, aromatic hydrocarbons such as benzene, toluene, and xylene, ethers such as diethyl ether, THF, and dioxane, alcohols such as ethanol, isozolo, 9-ol, etc. etc. or a mixture thereof as a solvent, at a reaction temperature of room temperature to 200°C, at normal pressure to 100 kg/
The hydrogenation reaction is carried out under a hydrogen pressure of cm2.

As a heterogeneous catalyst, a catalyst such as nickel, cobalt, radium, platinum, rhodium, or ruthenium is used alone or supported on a carrier such as silica, diatomaceous earth, alumina, or activated carbon, and the amount used is based on the weight of the polymer. 0.5~
10 vt% is suitable.

The reaction usually completes in 1 to 48 hours.

In the present invention, a compound having 2 to 4 phenol residues is used as an antioxidant, and is added in an amount of 0.01 to 5 parts by weight per 1 part by weight of hydroxyl group-containing hydrogenated liquid polyisoprene. Examples of such compounds are 2,2
'-Methylene-bis-(4-methyl-6-tert-butylphenol), 2,2'-methylene-bis-(4-
ethyl-6-tert-butylphenol), 4,4'
Bisphenol compounds such as -methylene-bis-(2,6-di-tart-butylphenol), 2,2'-methylene-bis-(6-αmethyl-benzyl-p-cresol), 1,3.5-) Trisphenol such as dimethyl-2,4,6-tris(3,5-di-t@rt-butyl-4-hydroxybenzyl)benzene, tris-(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, etc. compound, tetrakis-[methylene-3
Examples include tetrakisphenol compounds such as -(3',5'-dit@rt-7''thyl-4'-hydroxyphenyl)propionate comethane. Conventionally, it is most commonly used as a phenolic antioxidant. The monophenolic compounds mentioned above are completely unsuitable for the purposes of the present invention.

In addition, amine compounds, which are other types of antioxidants, have serious problems such as discoloration and staining, and are not suitable for the purpose of the present invention. If the amount of the compound having 2 to 4 phenol residues is less than 0.01 part by weight, no improvement in heat resistance will be obtained, and even if it exceeds 5 parts by weight, the amount added is less than 0.01 parts by weight. The effect is almost the same as in the case of , and it is not preferable because it actually impairs economic efficiency.

The composition of the present invention contains the hydroxyl group-containing hydrogenated liquid polyisoprene obtained as described above and a polyisocyanate compound. The content ratio of both is the ratio of incyanate groups to hydroxyl groups in polyisoprene, that is, NC010H.
It is in the range of 0.5 to 4. If this ratio is less than 0.5, the crosslinking density of the resulting adhesive will be too low and the cohesive force will be too low; if it exceeds 4, the crosslinking density will be too high, resulting in an adhesive with poor adhesive strength. In either case, it is not possible to obtain a pressure-sensitive adhesive composition with sufficient performance, such as when the pressure-sensitive adhesive composition becomes a sticky agent.

Here, the polyisocyanate compound is not particularly limited, and 1
Isocyanate compounds containing two or more isocyanate groups in the molecule are used. Examples include tolylene diisocyanate, phenylene diisocyanate, diphenylmethane diisocyanate, modified diphenylmethane diincyanate, dicyclohexylmethane diincyanate, and the like.

The adhesive composition of the present invention may contain a tackifier resin. Typical tackifier resins include chillin resins, terbe/phenol resins, rosin resins, aromatic hydrocarbon petroleum resins, alicyclic hydrocarbon petroleum resins, aliphatic hydrocarbon petroleum resins, Coumarone indene resin or phenolic resin may be mentioned. These tackifier resins may be used alone or in combination of two or more. The amount of hydrogenated liquid isoprene containing hydroxyl group is 1
5 to 250 parts by weight, preferably 20 parts by weight
~60 parts by weight. If the amount used is too small, it will not be possible to obtain an adhesive composition with sufficient tack and adhesive strength, while if it is too large, an adhesive composition with sufficient cohesive strength will not be obtained.

The adhesive composition of the present invention may further contain other additives, such as ultraviolet absorbers; pigments; softeners such as process oil, etc., as required.

The adhesive composition of the present invention is used by applying it to a substrate such as paper, cellophane, polyester, etc. and crosslinking it by heating. The temperature required for crosslinking is room temperature to 200°C, and the reaction time required for crosslinking is 0.1 to 50 hours. However, considering productivity, it is desirable to shorten the reaction time, and it is necessary to widen the reaction time under heating.
Preferably, the reaction is carried out at a temperature in the range of -150<0>C.

The adhesive composition of the present invention can be coated on a film of paper, cloth, polypropylene, polyester, vinyl chloride, or other plastic, and used in the form of a tape or sheet as an adhesive tape, adhesive label, or adhesive sheet. .

The present invention will be explained in more detail with reference to Examples below.

Example 1 Hexane Km-divinylbenzene 60 mrnol was completely dissolved, this was cooled to -10°C, and n-BuLl 13
0 mmol was added dropwise to produce m-di-lithiohexylbenzene, to which 2.2 mo of isogrene monomer was added dropwise.
1 was added and polymerized at 40°C. Then, 4 mol of ethylene oxide was added to the reaction system, and the resulting product was poured into a large amount of methanol to obtain a precipitate of liquid polyisoprene having hydroxyl groups at both ends. The molecular weight of the obtained polyisoprene was 2900.3.4 The number of hydroxyl groups in one molecule was 11q6.4 and 1.92.

After dissolving the obtained liquid polyisoprene in dioxane, each was heated at a hydrogen pressure of 3 using Ru-C (Ru 5%) as a catalyst.
The hydrogenation reaction was carried out at 0 kg/cm2. After the reaction, the catalyst is separated by filtration, and the hydrogenated liquid is obtained by vacuum drying. Liisoprene (1) was obtained.

The hydrogenation rate as determined by the iodine value was 85.

Various antioxidants were added to this hydrogenated liquid polyisoprene (I) according to the treatments shown in Table 1, and the obtained hydrogenated liquid pre-imprene was used to prepare an adhesive formulation according to the formulation shown in Table 1. The heat resistance was evaluated by measuring the adhesion performance and examining the change in performance when heated in an open environment at 180°C.

The results are shown in Table-2.

Below is the margin Example-2 40 mmol of m-novinylbenzene, n-B
Inzolene monomer was polymerized and hydrogenated in the same manner as in Example 1, except that uLi was changed to 90 mmol, and the molecular weight was 3950.
3.4 Bond amount is 10.5%, number of hydroxyl groups in water molecule is 1
．． Hydrogenated polyisoprene (It) having 94 hydroxyl groups and a hydrogenation rate of over 70 was obtained. This hydroxyl group-containing hydrogenated, fe-lisoprene is
G-tert-7''thyl-4'-hydroxyphenylpropionate comethane was blended according to the procedures shown in Table 3, and using this, an adhesive formulation was prepared according to the formulations shown in Table 3.

The performance and heat aging resistance of the adhesive were evaluated in the same manner as in Example-1.

Margins (Effects of the Invention) The present invention provides a pressure-sensitive adhesive composition that is excellent in heat aging resistance and weather resistance, and has sufficient adhesive performance.

Claims (1)

[Claims] (1) Molecular weight 700-7000, vinyl bond content 20% or less, 1.5 or more hydroxyl groups per molecule, and 40% or more of the carbon-carbon double bonds in the molecular chain are hydrogenated. Hydroxyl group-containing hydrogenated liquid polyisoprene; (2) phenol residue added in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the hydroxyl group-containing hydrogenated liquid polyisoprene;
-4 compounds, and (3) the ratio of hydroxyl groups to NCO groups in the hydroxyl group-containing hydrogenated liquid polyisoprene is 0.5 to
An adhesive composition comprising a polyisocyanate compound in an amount of 4 equivalents.