JPH0427253B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a curable composition that is stable at room temperature and can be rapidly cured by the action of heat or active energy rays as it is or after blending with a polymerization initiator. The present invention relates to a curable composition comprising a compound having two polymerizable unsaturated groups, a compound having at least two mercapto groups in one molecule, and a small amount of an alkali metal salt of a weak acid. It has long been known that unsaturated compounds and mercapto compounds produce polymers through radical addition reactions. In particular, a mixture of a compound having at least two polymerizable unsaturated groups in one molecule and a compound having at least two mercapto groups in one molecule, and adding an appropriate polymerization initiator as necessary. It is well known that it can be cured by heating or irradiation with active energy rays to give a cured product with good performance. However, this mixture is generally unstable and has the disadvantage of gradually increasing viscosity during storage and sometimes gelling, and the mixture yields a uniformly cured product after storage. Therefore, immediately before use, a compound having at least two polymerizable unsaturated groups in one molecule and a compound having at least two mercapto groups in one molecule are mixed for a short time until thickening occurs. The problem was that a curing operation had to be performed during the process. In particular, mixtures containing polymerization initiators are unstable;
It was essential to transfer the mixture to the curing operation in a short time. The inability of the mixture to withstand storage is inconvenient in terms of application, and various methods of improvement have been attempted up to now, but none of the methods has been fully satisfactory. Since the reaction between a compound having at least two polymerizable unsaturated groups in one molecule and a compound having at least two mercapto groups in one molecule is a radical addition reaction, general radical reaction inhibitors and It has been considered to incorporate benzoquinone, hydroquinone, picric acid, etc., which are known as retarders, into the mixture, but depending on the type of compound, curing may be poor at all, or even if curing occurs, these inhibitors and retardants may not be present. There are drawbacks such as the curing reaction becomes extremely slow due to the combination of agents and the cured product becomes colored. The present inventors have developed various methods for stably storing a mixture of a compound having at least two polymerizable unsaturated groups in one molecule and a compound having at least two mercapto groups in one molecule at room temperature for a long period of time. As a result of our investigation, we found that alkali metal salts of weak acids are extremely effective as stabilizers, and compositions containing them are stable for long periods of time at room temperature, with almost no reduction in the reaction rate between unsaturated groups and mercapto groups. , and found that it did not impair the physical properties of the cured product.
The present invention has now been completed. That is, the present invention provides a curable composition comprising a compound having at least two polymerizable unsaturated groups in one molecule, a compound having at least two mercapto groups in one molecule, and a small amount of an alkali metal salt of a weak acid. relating to things. In the present invention, the effect of adding an alkali metal salt of a weak acid is extremely remarkable, and although the details of its mechanism of action are not clear, the change in viscosity of the composition is significantly reduced by adding an alkali metal salt of a weak acid, and the composition is It is stable for a long period of time at room temperature, and the cured product obtained from this composition hardly changes its physical properties, so it has extremely high utility value industrially. The compounds used in the present invention having at least two polymerizable unsaturated groups in one molecule include vinyl groups, acryloyl groups, methacryloyl groups,
It is a compound having at least two polymerizable unsaturated groups in one molecule of one or more types selected from ally group and arylidene group. Specific examples include (a) Compounds having an acryloyl group: ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, propylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, Polypropylene glycol diacrylate, butanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, epoxy diacrylate, polyester diacrylate, polyether diacrylate, polyurethane diacrylate, poly Polyhydric acrylic esters such as siloxane diacrylate can be used. (b) Compounds having a methacryloyl group: ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, propylene glycol dimethacrylate, dipropylene glycol dimethacrylate, tripropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, Butanediol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol hexamethacrylate, epoxy dimethacrylate, polyester dimethacrylate, polyether dimethacrylate, polyurethane dimethacrylate, polysiloxane dimethacrylate, etc. Examples include polyhydric methacrylic acid esters. (c) Compounds having an allyl group diallyl succinate, diallyl adipate, diallyl phthalate, diallyl isophthalate, diallyl itaconate, diallyl fumarate, diallyl terephthalate, triallyl trimellitate, tetraallyl pyromellitate,
Examples include allyl esters such as triallyl isocyanurate, diethylene glycol diallyl carbonate, bisphenol A diallyl carbonate, and the like. (d) Compounds having a vinyl group Vinyl ethers such as ethylene glycol divinyl ether and bisphenol A diethoxy vinyl ether are mentioned. (e) Compounds having an arylidene group Diarylidenepentaerythritol, triarylidene sorbitol, diarylidene-2,
At least two molecules in one molecule, such as 2,6,6-tetramethylolcyclohexanone, etc. and (or) Examples include compounds having an unsaturated cycloacetal group represented by: The compounds (a) to (e) above having at least two polymerizable unsaturated groups in one molecule may be used in combination, and the mixing ratio is arbitrary. The compound having at least two mercapto groups (HS-) in one molecule is an aliphatic or aromatic mercaptan, such as dipentene dimercaptan, ethylcyclohexyl dimercaptan,
1,6-hexane dimercaptan, and ester compounds of mercapto compounds having a carboxyl group and polyhydric alcohols, such as thioglycolic acid or β-mercaptopropionic acid, esters of mercaptosuccinic acid and polyhydric alcohols,
For example, esterified products with trimethylolpropane and trimethylolethane, esterified products with pentaerythritol and dipentaerythritol,
Examples include compounds having a hydroxyl group at the carbon atom at the β-position relative to the methcapto group, compounds obtained by the reaction of an epoxy resin with hydrogen sulfide, and compounds obtained by the reaction of an epoxy resin with thioglycolic acid. It will be done. Among the above combinations of a compound having at least two polymerizable unsaturated groups in one molecule and a compound having at least two mercapto groups in one molecule,
A compound having at least two allyl groups in one molecule, a combination system of a compound having at least two allyl groups in one molecule and a compound having at least two (meth)acryloyl groups in one molecule,
A compound having at least two arylidene groups in one molecule, or a combination system of a compound having at least two arylidene groups in one molecule and a compound having at least two (meth)acryloyl groups in one molecule, Used as a compound having at least two polymerizable unsaturated groups in the molecule, and combining these with one
The combination with a compound having at least two mercapto groups in the molecule is particularly effective due to the combination of an alkali metal salt of a weak acid. The compound having at least two polymerizable unsaturated groups in one molecule and the compound having at least two mercapto groups in one molecule are mixed at room temperature or in a heated state, and by appropriate methods such as stirring, shaking, kneading, etc. uniformly mixed by suitable means. A compound having at least two polymerizable unsaturated groups in one molecule and 1
The mixing ratio with the compound having at least two mercapto groups in the molecule is 1:0.1 to 1:
2, preferably 1:0.2 to 1:1. If the mixing ratio is outside the above range, curing will be slow, which is not practical. Small amounts of surfactants, leveling agents, anti-yellowing agents, acid inhibitors, ultraviolet absorbers, coupling agents, etc. may be added to this mixture. Examples of the alkali metal salts of weak acids used in the present invention include salts of weak trout such as boric acid, silicic acid, carbonic acid, phosphoric acid, and ethylenediaminetetraacetic acid with alkali metals such as lithium, sodium, potassium, rubidium, and cesium. can give. Among these alkali metal salts of weak acids, monoalkali metal salts, dialkali metal salts, trialkali metal salts, tetraalkali metal salts of ethylenediaminetetraacetic acid, monoalkali metal salts of phosphoric acid, dialkali metal salts, and acid alkali metal salts. is preferable, and specific examples include ethylenediaminetetraacetic acid disodium salt,
Examples include tripotassium ethylenediaminetetraacetate, tetralithium ethylenediaminetetraacetate, sodium monohydrogen phosphate, lithium dihydrogen phosphate, and potassium phosphate. Further, in the present invention, a mixture or double salt of an alkali metal salt of a weak acid and an alkaline earth metal salt of a weak acid, such as trisodium ethylenediaminetetraacetic acid calcium salt, etc. can also be used. These alkali metal salts of weak acids may be used alone or in combination of two or more. The amount of the alkali metal salt of a weak acid is effective in a small amount relative to the total amount of the compound having at least two polymerizable unsaturated groups in one molecule and the compound having at least two mercapto groups in one molecule. However, if the amount of the alkali metal salt of a weak acid is extremely small, the effect is poor, while if the amount of the alkali metal salt of a weak acid is extremely large, the cured product may become cloudy or other inconveniences. Usually, it is 0.001 to 0.5% by weight, preferably 0.01% by weight, based on the total amount of the compound having at least two polymerizable unsaturated groups in one molecule and the compound having at least two mercapto groups in one molecule. Used within the range of ~0.1% by weight. The alkali metal salt of a weak acid may be added at the same time when mixing a compound having at least two polymerizable unsaturated groups in one molecule and a compound having at least two mercapto groups in one molecule. ,
It may be blended after mixing both of the above compounds, or
It may be added to either one of the above compounds and then mixed together. In addition, when synthesizing either one of the above compounds, a synthesis catalyst such as phosphoric acid is used, and after mixing both of the above compounds, this neutralized product is added to the total amount of the mixture of both compounds as the alkali metal salt concentration of the weak acid. Raw materials purified under conditions such that the concentration is 0.01 to 0.5% by weight may also be used. Among the above-mentioned alkali metal salts of weak acids, compounds having at least two polymerizable unsaturated groups in one molecule, compounds having at least two mercapto groups in one molecule, or a mixture thereof can be dissolved. Some have low solubility and are apparently dispersed, but both can improve stability. When using an alkali metal salt of a weak acid with low solubility, curing may be carried out while the alkali metal salt of a weak acid is dispersed, or the dispersed alkali metal salt of a weak acid may be removed by passing just before use. ,
It may be hardened using a liquid. To cure the composition of the present invention, the composition must be placed in a suitable mold or applied to a substrate, and then
Cured by heating or irradiation with active energy rays. Heat curing is carried out by placing the material in a suitable oven and heating it with hot air, or by irradiating it with infrared rays. In the case of curing with active energy rays, ultraviolet rays, X-rays,
It is cured by irradiation with gamma rays, electron beams, etc. When curing the composition, it is often effective to add an initiator for radical polymerization and a sensitizer. Polymerization initiators used when heating and curing the composition include benzoyl peroxide, azobisisobutyronitrile, diisopropyl peroxydicarbonate, tert-butyl hydroperoxide, cumene hydroperoxide,
Examples include dicumyl peroxide and tert-butyl peroxyoctoate. on the other hand,
Polymerization initiators used when the composition is cured by active energy rays, particularly UV irradiation, include benzoyl, benzyl, benzophenone,
Benzophenone tetratert-butyl perester, acetophenone, 2-hydroxy-3-
Sensitizers include benzoylpropane, benzoin methyl ether, benzoin isopropyl ether, 2-oxy-4-methoxybenzophenone, thioxanthone, methyl orthobenzyl benzoate, dimethoxyacetophenone, and the like. Depending on the type of compound, an acid catalyst such as polyphosphoric acid, phosphoric acid, trifluoroacetic acid, para-toluenesulfonic acid, boron trifluoride complex, tin chloride, or zinc chloride may be added and heated to accelerate curing. You can also do so. These polymerization initiators may be used alone or in combination with each other. The amount used is 0.01~ based on the total amount of the composition.
5% by weight, preferably 0.05-1% by weight. The curable composition of the present invention is stable for a long period of time at room temperature, hardly reduces the reaction rate between unsaturated groups and mercapto groups, and does not impair the physical properties of the resulting cured product, so it can be used for lenses, etc. It is useful for manufacturing cast products such as prisms and display displays, and as a coating agent and adhesive. Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 1 equivalent of triallyl isocyanurate (83.1 g)
and 1 equivalent (132.7 g) of trimethylolpropane trithiopropionate, and then add 0.1 ethylenediaminetetraacetic acid disodium salt to the mixture.
g was added and stirred vigorously to uniformly disperse the mixture. The resulting composition had a viscosity of 110°C at 25°C. The viscosity change of this composition when it was left at 25°C is as shown in Table 1, and almost no thickening was observed even after it was left for 30 days. On the other hand, when ethylenediaminetetraacetic acid disodium salt was not added to the mixture, thickening was already observed after one day of standing, and the mixture turned into a gel within 10 days.

[Table] 0.1% by weight of benzoyl peroxide was added to each of the as-prepared composition of Example 1 and the composition left for 30 days, and the mixture was spread on a glass plate in a thickness of 50 microns. coating and gradually increasing the temperature to 90
It was kept at ℃ for 2 hours to harden. All of the cured coatings had excellent adhesion to the glass plate, and the pencil hardness of each coating was 3H. From the above results, it has been confirmed that the mixture of triallyl isocyanurate and trimethylolpropane trithiopropionate is significantly stabilized by adding ethylenediaminetetraacetic acid disodium salt. Example 2 0.08g of phosphoric acid was dissolved in 10g of water and potassium bicarbonate was added to adjust the pH to 7.0. Diarylidenepentaerythritol 96g (1
equivalent amount) and then heated to evaporate water to uniformly mix potassium phosphate with diarylidenepentaerythritol. This diarylidene pentaerythritol to pentaerythritol tetrathioglycolate 108
(1 equivalent) and 198 g (2 equivalents) of trimethylolpropane triacrylate and heated at 60°C for 30 minutes.
After holding for a minute, 0.9 g of benzoin isopropyl ether (photopolymerization initiator) was added to obtain a photocurable composition. When this composition was stored at 25°C away from light, almost no increase in viscosity was observed even after being left for 60 days as shown in Table 2. On the other hand, when a photocurable composition was prepared using diarylidenepentaerythritol without the addition of potassium bicarbonate neutralized phosphoric acid, the viscosity did not increase even when stored at 25°C away from light. Significantly, the composition gelled after standing for about 30 days.

[Table] Omitted The composition of Example 2 immediately after preparation and the composition after being left for 30 days were respectively poured into glass molds and irradiated with ultraviolet rays from above and below using a high-pressure mercury lamp for 30 seconds.
A colorless, transparent and uniform cured product was obtained from each composition. Example 3 123 g (1 equivalent) of diallyl orthophthalate, 212 g of trimethylolpropane trimethacrylate
(1 equivalent) and 214 g (1.8 equivalent) of trimethylolpropane trithioglycolate, and then 2.5 g of 2-hydroxy-3-benzoylpropane as a photopolymerization initiator was added to the mixture and uniformly dissolved. Then add 0.5 dilithium phosphate to this mixture.
g was added and stirred and dispersed. The resulting composition was stable, and when left at 30° C. without light, it hardly thickened even after being left for 30 days as shown in Table 3. On the other hand, when dilithium phosphate was not added to the mixture, significant thickening was already observed after 7 days of standing, and gelation occurred after 30 days of standing.

[Table] omitted
From the above results, it was confirmed that dilithium phosphate has an excellent stabilizing effect on storage stability. In addition, when the composition immediately after preparation of Example 3 and the composition after being left for 30 days were applied to a thickness of 50 microns on a glass plate and irradiated with ultraviolet rays from a 30W high-pressure mercury lamp at a distance of 15cm, The composition was completely cured in 10 seconds, and a transparent cured film was obtained. Example 4 Diarylidenepentaerythritol 106g (1
After mixing 108 g (1 equivalent) of pentaerythritol tetrathioglycolate at 80°C for 60 minutes, 2.1 g of benzophenone was added as a photopolymerization initiator.
was added and stirred to dissolve. Next, when ethylenediaminetetraacetic acid (abbreviated as EDTA) or alkali metal salt of phosphoric acid shown in Table 4 was added to this liquid mixture and the mixture was left at 40°C, the viscosity change was as shown in Table 4. Almost no thickening was observed even after leaving it for 30 days.

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Claims (1)

[Claims] 1. A curable composition comprising a compound having at least two polymerizable unsaturated groups in one molecule, a compound having at least two mercapto groups in one molecule, and a small amount of an alkali metal salt of a weak acid.