JPH0479393B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is characterized by a method of hardening by absorbing moisture in the air.
The present invention relates to a moisture-curable adhesive composition useful as an adhesive for moisture-curable adhesive tapes. [Prior Art] In order to make adhesive tapes hardenable, various proposals have been made regarding adhesives, but adhesives that use a slight epoxy adhesive and are heated and cured over a long period of time have been developed. Tapes have only been put to practical use, and adhesive tapes using adhesives that harden within a relatively short period of time at room temperature have not yet appeared on the market. There are various methods for curing adhesives that harden at room temperature (e.g., anaerobic curing method, light curing method), but they can be stored safely for a long time by eliminating the influence of moisture during storage, and can be stored safely after use. If it hardens, moisture-curing adhesives are considered to be the most convenient to use, since they can be applied to any object. The most typical moisture-curable polymers or oligomers are so-called one-component solvent solutions of polyethers and polyesters having isocyanate groups in less than one molecule.
These are used as paints and adhesives. In addition, to increase the adhesive strength of adhesive tape,
Modification of conventional adhesives with polyvalent isocyanates has also been carried out. [Problems to be Solved by the Invention] However, these conventional polymers and oligomers having isocyanate groups do not necessarily have sufficient storage stability due to the reactivity of the isocyanate groups. If a polymer or oligomer contains enough isocyanate groups to be cured by moisture, if the polymer or oligomer containing this isocyanate group absorbs moisture during the steps of applying it to a substrate and removing the solvent,
The problem is that the adhesive tape's shelf life is significantly impaired and its commercial value is completely lost. In addition, in the manufacturing process of the adhesive tape, it is difficult to make it moisture-curable as a practical matter if the content of isocyanate groups is such that it does not affect practical use. Complete drying of the entire manufacturing process is expensive, if not impossible, and undesirable. The present inventors used isocyanatoethyl methacrylate manufactured by Dow Chemical Company, which has an isocyanate group in the molecule, as one component of the monomer, and used this and other monomers (e.g., butyl acrylate, 2-ethylhexyl acrylate, etc.). ) was solution copolymerized to produce a polymer having an isocyanate group in the side chain, and it was found that the synthesis of the copolymer was easy if a sufficiently dehydrated solvent was used, and that the isocyanate group was a monomer. It has been found that if the amount is 20 mol% or more of the total amount, an adhesive polymer capable of moisture curing can be obtained. However, the stiffness copolymer is unstable and has the disadvantage that it gels in about a week even in a system in which a moisture absorbent such as a molecular sieve is added. In addition, the moisture-curable adhesive tape obtained by applying the isocyanate group-containing copolymer to the base film immediately after production obtained by the above method is coated with a silica gel moisture-proofing agent in a moisture-proof bag made from a laminate film of aluminum and polyethylene. Even if it was sealed tightly, it lost its tackiness the next day and could not function as an adhesive at all. From this point of view, the present inventors have conducted various studies in order to obtain a more stable moisture-curable adhesive tape, and as a result, the present inventors have developed an unsaturated isocyanate having an acryloyl group or a methacryloyl group and a copolymerizable isocyanate with the unsaturated isocyanate. If a mixture of monomers is applied to a base material and then irradiated with active energy rays in the absence of air to form a polymer on the base material, the adhesive tape will be less affected by humidity when manufacturing the adhesive tape. I came to know that it has a good shelf life even after cooking. This method is an extremely useful method for producing moisture-curable adhesive tapes if there is an apparatus for irradiating active energy rays. However, this method cannot be applied in cases where a device for irradiating active energy rays is not available, and therefore there may be a need for a moisture-curable adhesive composition that can be applied to commonly used coating devices. Generally, if the isocyanate group in the polymer side chain is 20 mol% or less, preferably 10 mol% or less, based on the total of 100 mol% of the unsaturated isocyanate and the monomers copolymerizable with the unsaturated isocyanate. By adding a molecular sieve, it can be stored fairly safely, but at this level, the curability and physical properties after curing are insufficient for a moisture-curing type. [Means for solving the problem] However, as a result of further research, the present inventors found that in order to obtain a practical moisture-curing adhesive, the standard amount of isocyanate groups per unit weight is However, this does not depend solely on the isocyanate groups of the polymer, but rather it is possible to use a tackifier having isocyanate groups in combination with a polymer having isocyanate groups in the composition to provide sufficient moisture curing. The present invention was completed based on the knowledge that a moisture-curable pressure-sensitive adhesive composition with excellent preservability, adhesiveness, and adhesive strength can be obtained if it contains an isocyanate group. That is, the present invention comprises (1) (a) 1 to 30 mol% of an unsaturated isocyanate having an acryloyl group or a methacryloyl group;
A moisture component comprising a polymer having an isocyanate group in its side chain obtained by reacting the unsaturated isocyanate with 70 to 99 mol% of copolymerizable monomers, and (2) a tackifying agent having an isocyanate group. The present invention relates to a curable adhesive composition. As the unsaturated isocyanate having an acryloyl group or a methacryloyl group (hereinafter abbreviated as (meth)acryloyl group) used in the present invention, "isocyanate ethyl methacrylate" commercially available from Dow Chemical Company is used. is useful. In addition, a reaction product of a diisocyanate and an unsaturated monoalcohol having a (meth)acryloyl group in which the molar ratio of isocyanate groups to hydroxyl groups is practically 1:1 can also be used. Examples of the diisocyanate include 2,4-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, paraphenylene diisocyanate,
1,5-naphthylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, 1,
Examples include 6-hexamethylene diisocyanate and isophorone diisocyanate. Examples of unsaturated monoalcohols for introducing (meth)acryloyl groups by reacting with these diisocyanates include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxyethyl acrylate.
Examples include hydroxypropyl methacrylate. In addition to these unsaturated monoalcohols having a (meth)acryloyl group, reaction products of monoepoxy compounds and acrylic acid or methacrylic acid can also be used, such as phenyl glycidyl ether, Examples include reaction products of butyl glycidyl ether, octyl glycidyl ether or styrene oxide and acrylic acid or methacrylic acid. An example of a reaction product between phenyl glycidyl ether and acrylic acid is represented by the following formula. When reacting diisocyanate and unsaturated monoalcohol, it is advantageous to use organic tin compounds, tertiary amines, etc., which are usually used as urethanization catalysts, and in order to prevent polymerization during the reaction. It is preferable to include a commonly used polymerization inhibitor. For example, when the reaction is carried out using 2,4-tolylene diisocyanate as the diisocyanate and 2-hydroxyethyl acrylate as the unsaturated monoalcohol having a (meth)acryloyl group, the following formula is obtained. The unsaturated isocyanate shown is formed. However, the unsaturated isocyanate synthesized from a diisocyanate and an unsaturated monoalcohol is not a single compound as shown in the above formula, and the following diacrylates may coexist. The presence of this diacrylate causes gelation trouble during polymer synthesis, so it is necessary to prevent its formation. In order to prevent the formation of diacrylate, the reaction may be carried out using a slightly excess amount of diisocyanate relative to the unsaturated monoalcohol. Monomers that are copolymerized with an unsaturated isocyanate having a (meth)acryloyl group to form a polymer having an isocyanate group in the side chain are It is desirable that the glass transition temperature is 30°C or less. Monomers constituting polymers with glass transition temperatures higher than 30°C, such as styrene, vinyltoluene, methyl methacrylate, acrylonitrile, etc., may be used in combination with monomers that polymerize to give polymers with glass transition temperatures below 30°C. Although it may be used to increase the adhesive strength, it is not preferable to mix it alone with an unsaturated isocyanate having a (meth)acryloyl group because it reduces the tackiness of the adhesive composition. Examples of monomers having a glass transition temperature of 30°C or lower when polymerized to form a polymer include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, and n-methacrylate. Examples include phtyl, 2-ethylhexyl methacrylate, decyl methacrylate, lauryl methacrylate, vinyl acetate, vinyl propionate, and the like. The ratio of the unsaturated isocyanate having a (meth)acryloyl group and the monomers is 1 to 30 mol% of the unsaturated isocyanate and 70 to 99 mol% of the monomer, preferably 5 to 5 mol% of the unsaturated isocyanate.
~20 mol% and monomers 80-95 mol%. If the usage ratio of the unsaturated isocyanate having a (meth)acryloyl group is less than 1 mol%, the effect of adding the unsaturated isocyanate is small and the moisture curing property is insufficient; If the proportion of isocyanate used is more than 30 mol %, it is not necessary as a practical matter because the adhesive also contains isocyanate groups. Polymers with isocyanate groups in their side chains are
Generally, it is produced by solution polymerizing an unsaturated isocyanate having a (meth)acryloyl group and a monomer copolymerizable with the unsaturated isocyanate. The tackifier having an isocyanate group used in the present invention includes, for example, (1) a saturated or unsaturated alkyd with 2
(2) Polyethers that similarly have two or more hydromexyl groups; (3) Polyhydroxyl oligomers made by reacting novolak or resol with monoepoxide. Examples include isocyanates such as Among the above, Alkyd is made into an isocyanate, and by changing the type and amount of the polyhydric alcohol and polybasic acid components, Alkyd has various physical properties ranging from liquid prepolymers to high softening point resins. It is best suited for the purposes of the present invention in that it can vary widely. Isocyanation of an alkyd can be easily carried out by dissolving the alkyd in a monomer and adding it to the isocyanate. Examples of polyhydric alcohol components constituting the alkyd include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, trimethylolpropane, glycerin, pentaerythritol, bisphenol A propylene oxide adduct, and pisphenol A ethylene oxide. Examples include additives. Examples of polybasic acid components include phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, maleic anhydride, fumaric acid, itaconic acid, tetrahydrophthalic anhydride, and hexahydrophthalic anhydride. Examples include phthalic anhydride, endomethylenetetrahydrophthalic anhydride, and trimellitic anhydride. When using a trihydric or higher polyhydric alcohol, a monobasic acid may be used together, and when a polybasic acid is used, a monoalcohol can also be used together. The proportion of the tackifier having an isocyanate group is determined by
10 to 200 parts by weight, preferably 30 parts by weight per 100 parts by weight
~120 parts by weight. If the proportion of the tackifier having an isocyanate group is less than 10 parts by weight, it is difficult to obtain the effects of the present invention, whereas if the proportion is more than 200 parts by weight, the tackiness is good, but the initial adhesion is poor. It is easy to lose power. The moisture-curable adhesive composition of the present invention is prepared by mixing a polymer having an isocyanate group in its side chain and a tackifier having an isocyanate group, and both components are mixed immediately before use. It is preferable. Adding an additive having an anti-moisture absorption effect, such as a molecular sieve, to the mixture of both components is extremely useful in improving the stability of the moisture-curable pressure-sensitive adhesive composition. Furthermore, the moisture-curable adhesive composition of the present invention includes:
Of course, various additives such as attachment/detachment agents and fillers can be added as necessary. [Effects of the Invention] The moisture-curable adhesive composition of the present invention has adhesive properties,
It has excellent preservability and adhesive strength, and is particularly suitable for use as an adhesive for moisture-curing adhesive tapes. [Example] Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 [Synthesis of polymer (A) having an isocyanate group in the side chain] In a 1 L separable flask equipped with a stirrer, a reflux condenser with a moisture-proof device, a thermometer, and a dropping funnel, 115 g of butyl acrylate, 115 g of methyl ethyl ketone, After charging 0.6g of azobisisobutyronitrile, isophorone diisocyanate was prepared at a temperature of 60℃.
68 g of an unsaturated isocyanate having an acryloyl group (50% solution in methyl ethyl ketone) synthesized from 222 g (1 mole) and 116 g (1 mole) of 2-hydroxyethyl acrylate was added dropwise over about 1 hour.
During the dropping, the temperature was maintained at 60°C by cooling as necessary. Next, while keeping the temperature at 60℃, the polymerization rate was increased.
After continuing the reaction until it reached 95% or more, 0.05 g of hydroquinone was added to stop the reaction. As a result of infrared analysis,
The presence of free isocyanate groups in the product was confirmed. A methyl ethyl ketone solution (polymer content: about 50% by weight) of the polymer (A) having an isocyanate group in its side chain was obtained in the form of a pale yellow, slightly viscous liquid (viscosity: about 40 poise). [Polyester having isocyanate groups (B)
Synthesis] 170 g of propylene glycol and 292 g of adipic acid were placed in a 1 liter three-necked flask equipped with a stirrer, a fractionating condenser, and a gas inlet tube with a thermometer. esterification, then esterification at 210-220℃ for 16 hours, and finally 10-15mm excluding the fractionation condenser
The pressure was reduced to Hg for 1 hour to synthesize a hydroxyl polyester with an acid value of 1.4 and a hydroxyl value of 64.4. The resulting hydroxyl polyester has a Hazen color number of 500
It had a viscous syrup-like consistency. After dissolving 100 parts by weight of this hydroxyl polyester in 100 parts by weight of methyl ethyl ketone, 26 g of 2,4-tolylene diisocyanate was added and the mixture was heated and stirred at 60°C for 3 hours.
As a result of infrared analysis, disappearance of free hydroxyl groups was observed. A methyl ethyl ketone solution of polyester (B) having a solid content of about 55% by weight and having isocyanate groups was obtained as a reddish brown and viscous solution. A pressure-sensitive adhesive composition is prepared by mixing 100 parts by weight of a methyl ethyl ketone solution of a polymer (A) having an isocyanate group in its side chain, 100 parts by weight of a methyl ethyl ketone solution of a polyester (B) having an isocyanate group, and 3 parts by weight of a molecular sieve. was prepared. As a test piece, the adhesive composition was applied to a 100 mm long end of a steel plate with a length of 150 mm, a width of 25 mm, and a thickness of 2 mm.
After removing the solvent at 300 mmHg, a Tetron film with a thickness of 50 μm was crimped. The physical properties immediately after application and after standing overnight are shown in Table 1, confirming that it is useful as a cured adhesive.

[Synthesis of polymer (C) having isocyanate groups in side chains]

In a 1 L separable flask equipped with a stirrer, reflux condenser, thermometer with gas inlet tube, and dropping funnel, add 276 g of 2-ethylhexyl acrylate, 16 g of acrylonitrile, 31 g of isocyanate ethyl methacrylate manufactured by Dow Chemical Company, and dehydrated methyl ethyl ketone. When 323 g and 3.5 g of azobisisobutyronitrile were charged and polymerized for 10 hours at the boiling point of methyl ethyl ketene in a nitrogen gas stream,
The polymerization rate was almost 100%. After adding 0.06g of hydroquinone to stop polymerization,
Infrared analysis of the product confirmed the presence of free isocyanate groups. A methyl ethyl ketone solution (polymer content: about 50% by weight) of the polymer (C) having an isocyanate group in a side chain was obtained, having a viscosity of about 30 poise and a pale yellowish brown color. [Synthesis of polyetherified phenol resin (D) having an isocyanate group] In a 1 L separable flask equipped with a stirrer, a dropping funnel, a reflux condenser with a moisture-proof device, and a thermometer, resol-type paratertiary butyl phenol resin (approx. After uniformly dissolving 3-nuclear resin, melting point approximately 75℃) and 50% by weight of toluene, 1 mole of ethylene oxide was added to the phenolic hydroxyl group under triethylamine catalyst, and a toluene solution of polyhydroxylated phenolic resin (solid A hydroxyl number of 269) was obtained. In another identical apparatus, add isophorone diisocyanate.
150g, toluene 159g, dibutyltin dilaurate
After charging 0.5 g and 10 g of molecular sieve and mixing them uniformly, 200 g of the toluene solution of the polyhydroxylated phenolic resin was added dropwise to this mixture at a temperature of 50 to 60°C. After the dropwise addition was completed, the reaction was carried out at 60°C for 3 hours, and as a result of infrared analysis, it was determined that the free hydroxyl groups had disappeared. A toluene solution of polyetherified phenolic resin (D) having isocyanate groups (resin content approximately 50
% by weight) was obtained with a pale yellowish brown color and a viscosity of about 260 poise. A pressure-sensitive adhesive composition was prepared by mixing 100 parts by weight of a methyl ethyl ketone solution of the polymer (C) having an isocyanate group with 100 parts by weight of a toluene solution of the polyetherified phenolic resin (D) having an isocyanate group. A nonwoven fabric made of polyethylene terephthalate having a thickness of 0.2 mm was impregnated with this adhesive composition, and then placed in a vacuum desiccator equipped with dehumidification, and the solvent was removed under reduced pressure of about 200 mmHg. The resulting double-sided adhesive tape was cut into pieces of 25 mm x 13 mm and adhered to a polished steel plate measuring 150 mm x 25 mm x 3 mm using a sander arch, and then the adhesive strength by tensile shearing was measured. The same procedure was also carried out when the polymer (C) having an isocyanate group and the polyetherified phenol resin (D) having an isocyanate group were used alone. As shown in Table 2, only the pressure-sensitive adhesive composition of the present invention exhibited well-balanced physical properties, and its practicality was recognized.

【table】

Claims (1)

[Claims] 1. (a) 1 to 3 mol% of an unsaturated isocyanate having an acryloyl group or a methacryloyl group, and (b) monomers copolymerizable with the unsaturated isocyanate.
A moisture-curable pressure-sensitive adhesive composition comprising a polymer having an isocyanate group in its side chain obtained by reacting 70 to 99 mol% with a tackifier having two isocyanate groups.