JPS6315933B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a composition containing a liquid polychloroprene-based isocyanate prepolymer as a main component. Various curable liquid chloroprene polymer compositions have been known. The present inventor conducted research with the aim of obtaining a liquid polymer composition having a polychloroprene main chain structure that exhibits better properties than conventional chloroprene rubber when cured by vulcanization. A cross-linking agent and a polychloroprene vulcanization accelerator are added to a liquid polychloroprene-based isocyanate prepolymer made from a liquid chloroprene-based polymer having two or more hydroxyl groups and a number average molecular weight in the range of 500 to 10,000. The present invention was achieved by discovering that a composition that can achieve the above object can be obtained by combining the above objects. That is, an object of the present invention is to provide a liquid chloroprene-based polymer composition that can be cured to form a chloroprene-based elastomer with excellent ozone resistance, and this object is achieved by the configuration of the present invention described below. Ru. The present invention uses a liquid chloroprene polymer having an average of two or more hydroxyl groups in the molecule and a number average molecular weight in the range of 500 to 10,000, and reacts this liquid chloroprene polymer with a difunctional isocyanate compound. Curing is carried out by adding a crosslinking agent and a polychloroprene vulcanization accelerator in an amount sufficient to react with 0.8 to 1.1 equivalents of the isocyanate groups in the prepolymer to the liquid polychloroprene-based isocyanate prepolymer obtained by The present invention provides a liquid polychloroprene-based isocyanate prepolymer composition that can form a chloroprene-based elastomer with excellent ozone resistance. The present invention will be described in more detail below. The liquid chloroprene polymer used in the present invention has an average of two or more hydroxyl groups in the molecule,
It has a number average molecular weight in the range of 500 to 10,000, and its production methods include radical copolymerization of chloroprene or chloroprene and a monomer copolymerizable with it using hydrogen peroxide, and 1-chlorobutadiene. - A method of obtaining a liquid chloroprene polymer obtained by radical copolymerizing 1,3 with chloroprene or a monomer copolymerizable therewith with a tertiary amine compound having a hydroxyl group; There are methods such as radical copolymerization of copolymerizable monomers with acrylates or methacrylates having hydroxyl groups, but from the viewpoint of industrial ease of implementation, chloroprene or chloroprene and monomers copolymerizable therewith are copolymerized with hydroxyl groups. A method of radical copolymerization with acrylate or methacrylate is preferred. The hydroxyl group-containing acrylate or methacrylate used in producing this liquid copolymer has the following formula:

[Formula] (where n is an integer of 1 or 2, and R is a hydrocarbon group having 2 or 3 carbon atoms) is preferred, and 2-hydroxyethyl acrylate, 2
-Hydroxyethyl methacrylate, etc., but are not limited thereto. If the number average molecular weight of the liquid chloroprene-based polymer used is less than 500, it will be difficult to introduce an average of two or more hydroxyl groups into the molecule, and the liquid polychloroprene-based isocyanate prepolymer will have good physical properties even after curing. It cannot be made into a cured product. On the other hand, if the number average molecular weight exceeds 10,000, it will no longer be a liquid polymer with low viscosity at room temperature, and will be extremely difficult to handle during use even as an isocyanate prepolymer. Further, even if the number average molecular weight is in the range of 500 to 10,000, if the average number of hydroxyl groups in the molecule is less than 2, a good cured product cannot be obtained even as an isocyanate prepolymer. This isocyanate prepolymerization of liquid chloroprene-based polymers can be carried out in the presence or absence of a solvent, but in the presence of a solvent, hydrocarbons or esters that do not have active hydrogen that react with hydroxyl groups or isocyanate groups can be used. , ketone, ether,
It is carried out by reacting a difunctional isocyanate compound and a liquid chloroprene polymer at a temperature of 25 to 100°C using a solvent such as an amide, a halogenated hydrocarbon, or a mixture thereof. This isocyanate prepolymerization reaction is usually carried out by adding 1.5 to 3.0, preferably 1.9 to 2.2 equivalents of isocyanate groups per equivalent of hydroxyl groups in the liquid chloroprene polymer. There are no particular limitations on the bifunctional isocyanate compound used in the isocyanate prepolymerization reaction, but examples include 2,4- and 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and 4,4'- Diphenyl diisocyanate, 1,5'-naphthalene diisocyanate,
Aromatic diisocyanates such as orthotolidine isocyanate, aliphatic diisocyanates such as 1,6-hexamethylene diisocyanate, 1,3- and 1,4-cyclohexyl diisocyanate,
and mixtures thereof are used. Among these, aromatic compounds are particularly preferred from the viewpoint of ozone resistance and abrasion resistance of the chloroprene elastomer obtained by post-curing a liquid polychloroprene isocyanate prepolymer. Next, the crosslinking agent used when curing the liquid polychloroprene isocyanate prepolymer to produce a chloroprene elastomer with excellent ozone resistance is an active hydrogen compound that can react with the free isocyanate groups in the prepolymer. Diamines and diols are preferred, but more highly functional ones can also be used. Examples of diamines include 4,4'-
Diaminodiphenylmethane, 3,3'-dichloro-
4,4'-diaminodiphenylmethane, 0-, m-
or aromatic diamines such as p-phenylenediamine and derivatives or mixtures thereof; aliphatic diamines such as hydrazine, ethylenediamine, trimethylenediamine, piperazine, hexamethylene-1,6-diamine and mixtures thereof. Examples of diols include ethylene glycol, propylene glycol, propane 1,3-diol, 1,4-butanediol, 1,4-butenediol, 2-ethyl-1,3-hexanediol, hydroquinone-bis-(2- (hydroxyethyl)-ether, analogs thereof, mixtures thereof, and the like. Alternatively, a preferred diamine and diol can be mixed to form a crosslinking agent. Furthermore, polyols such as trimethylolpropane and pentaerythritol are also effective. The equivalent ratio of the effective functional group of the crosslinking agent to the NCO group in the liquid chloroprene-based isocyanate prepolymer is
It ranges from about 0.8 to 1.1, preferably from 0.90 to
It is 1.05. Furthermore, when curing a liquid polychloroprene isocyanate prepolymer to produce a chloroprene elastomer with excellent ozone resistance, zinc white, magnesia, etc. are used as polychloroprene vulcanization accelerators in addition to the crosslinking agent. Polyvalent metal oxides and those having no active hydrogen that can react with isocyanate groups in liquid polychloroprene-based isocyanate prepolymers, such as xanthate-based ones such as zinc butyl xanthate, are preferred. These polychloroprene vulcanization accelerators have the function of forming cross-linkages of polychloroprene units in the liquid polychloroprene-based isocyanate prepolymer. Furthermore, polyvalent metal oxides such as zinc white and magnesia are effective because they capture hydrogen chloride generated during heating from the chloroprene unit and reduce the progress of deterioration. The amount of these polyvalent metal oxides added is 1 to 30 parts by weight per 100 parts by weight of the liquid polychloroprene-based isocyanate prepolymer. If the amount is less than this, a good cured product cannot be obtained, and if it exceeds 30 parts by weight, the practical performance of the cured product tends to deteriorate. When a vulcanization accelerator such as zinc butyl xanthate is used, the amount added is in the range of 0.1 to 5 parts by weight per 100 parts by weight of the liquid polychloroprene isocyanate prepolymer.
If it is less than 0.1 part, it will not substantially function as a vulcanization accelerator, and if it exceeds 5 parts, there will be no functional difference and it will be economically disadvantageous, meaning that it is practically meaningless. The above-mentioned liquid polychloroprene-based isocyanate prepolymer composition can proceed with the curing reaction at temperatures ranging from room temperature to high temperatures, but usually at temperatures of 150°C.
It is about ℃. In order to further advance the curing reaction, organic tin compounds such as dibutyltin dilaurate and tin octylate, tertiary amines such as triethylamine and triethylenediamine, and 1,8-diazabicyclo(5,4,0) are used as catalysts for the curing reaction.
- Cyclic amidine compounds such as undecene and its organic acid salts can be used as appropriate. The present invention provides a composition capable of providing a cured product exhibiting superior ozone resistance compared to conventional chloroprene-based elastomers only by adopting the above configuration.
This is achieved by cross-linking the liquid polychloroprene-based isocyanate prepolymer with a cross-linking agent by forming urethane bonds, urea bonds, and allophanate and biuret bonds, and at the same time, the polychloroprene units are also cross-linked and cross-linked with a vulcanization accelerator. If any one of these elements is missing, a good cured product cannot be obtained. The elastic body formed from this composition not only has excellent ozone resistance, but also has excellent abrasion resistance, hot water resistance, solvent resistance, weather resistance, flame retardancy, and chemical resistance. It has excellent properties such as hardness, heat resistance, and adhesiveness, so it can be used for a variety of purposes. For example, lining materials, potting materials, sealing materials, waterproof coating materials, adhesives,
Suitable for applications such as cast molded products and sponge materials. It is also possible to add isocyanate prepolymers of various polyether polyols and polyester polyols to the composition within a range that does not reduce the performance of the cured product formed as a chloroprene-based elastomer. Furthermore, if necessary for practical purposes, ordinary compound ingredients such as titanium dioxide, calcium carbonate, silica, clay, fillers such as carbon black, petroleum oils, phthanolic acid esters,
Softeners such as tars, resins, bituminous substances, and solvents as compound viscosity modifiers may be included. EXAMPLES Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these in any way. All amounts used in the examples are shown on a weight basis, and the following liquid chloroprene-based polymers were used including the comparative examples. Polymer 1: Obtained by radical polymerization of 88 parts of chloroprene, 5 parts of 2,3-dichlorobutadiene-1,3, and 7 parts of 2-hydroxyethyl acrylate in a toluene solvent at 50°C in the presence of 1.6 parts of 2-mercaptoethanol. Liquid polymer. Burdskfield viscosity 210,000 centipoise measured at 25°C. Number average molecular weight 5640. Hydroxyl group content 0.657%.
Average hydroxyl functionality in the molecule 2.18. Polymer 2: Liquid polymer obtained by radical polymerization of 88 parts of chloroprene and 12 parts of 2-hydroxyethyl methacrylate in the presence of 5.7 parts of n-dodecylmercaptan at 50°C in a toluene solvent. Burdskfield viscosity 115,000 centipoise measured at 25°C. Number average molecular weight 4970. Hydroxyl group content 0.797%.
Average hydroxyl functionality in the molecule is 2.33. Polymer 3: A liquid polymer obtained by radical polymerization of 95 parts of chloroprene and 5 parts of 2-hydroxyethyl methacrylate in the presence of 2.5 parts of 2-mercaptoethanol in a benzene solvent at 50°C. Burdskfield viscosity 59,000 centipoise measured at 25°C. Number average molecular weight 3900. Hydroxyl group content 0.73%.
Average hydroxyl functionality in the molecule is 1.67. The number average molecular weight of the polymer was measured using an everiometer, and the hydroxyl group content was measured using an acetyl chloride method. The average hydroxyl functionality in the molecule was obtained by dividing the number average molecular weight by the hydroxyl equivalent molecular weight determined from the hydroxyl group content using the following formula. Hydroxyl group equivalent molecular weight = 17.0 x 100/% hydroxyl group content Analysis of isocyanate content in the following examples was conducted according to the purity analysis method (dibutylamine method) described in JISK1556 Tolylene diisocyanate test method. Example 1 (Test No. 1) 100 parts by weight of Polymer 1 was accurately weighed into a separable flask equipped with a stirring bar, thoroughly dried and purged with nitrogen, and diphenylmethane diisocyanate was added to it.
Weighed and added so that NCO/OH = 2.2, and heated to 100℃.
The mixture was stirred and reacted for 5 hours. The isocyanate group content in the obtained liquid polychloroprene-based isocyanate prepolymer was 1.78%. This liquid polychloroprene-based isocyanate prepolymer is designated as A. Based on 100 parts by weight of this prepolymer A, 5 parts of zinc white and 3 parts in an amount corresponding to NH ₂ /NCO = 0.95,
3'-dichloro-4,4'-diaminodiphenylmethane was mixed with a paint mill, added at 100℃ for 1 hour, cured at 120℃ for 2 hours, and then heated to 50% at 20℃.
The physical properties of the chloroprene elastomer obtained by aging under humidity for 7 days are 100% modulus 73 (Kg/cm ² ), tensile strength 122 (Kg/cm ² ), elongation 280 (%), and hardness 87.
(JIS), ozone resistance 200pphm, 40℃, 20%, stretching
No cracking occurred for 168 hours. Example 2 (Test Nos. 2 to 5) Polymer 2 was prepolymerized in the same manner as in Example 1. The isocyanate group content in the obtained liquid polychloroprene-based isocyanate prepolymer was 2.10%. This liquid polychloroprene-based isocyanate prepolymer is designated as B. For 100 parts by weight of this prepolymer B, zinc white,
Varying amounts of zinc butyl xanthate and 1,4-butanediol were mixed in a paint mill, cured for 3 hours at a temperature of 100°C, and then aged for 7 days at a temperature of 20°C and a humidity of 50%. Table 1 shows the physical properties of the chloroprene-based elastomer. Note that Test No. 5 is a comparative example. Example 3 (Test No. 6) A compound prepared by blending liquid polychloroprene isocyanate A in a paint mill according to the following formulation was poured into a mold with a thickness of 2 mm, and heated at a temperature of 100°C for 1 hour. Press hardened, then released from the mold and heated in a gear oven at a temperature of 120℃ for 2 hours.
Table 2 shows the physical properties of the chloroprene-based elastomer obtained by aging for 7 days at a temperature of 20° C. and a humidity of 50% after curing by heating for a period of time. The results shown here also indicate that the chloroprene-based elastomer obtained from the composition of the present invention has excellent ozone resistance.

【table】

【table】

[Table] Comparative Example (Test No. 7) Polymer 3 was made into a prepolymer in the same manner as in Example 1. The isocyanate group content in the obtained liquid chloroprene-based isocyanate prepolymer is
It was 1.94%. This prepolymer 100
Based on parts by weight, 5 parts of zinc white and NH ₂ /NCO=
3,3'-dichloro-4,4'- in an amount corresponding to 0.95
Mix diaminodiphenylmethane in a paint mill, cure at 100℃ for 1 hour, and then cure at 120℃ for 2 hours.
The cured sheet obtained by aging at 50% humidity for 7 days had a tacky surface, a sticky feel, and was poorly cured. Its physical properties are 100%
The modulus was 11 (Kg/cm ² ), the tensile strength was 25 (Kg/cm ² ), the elongation was 150 (%), and the hardness was 38 (JIS K-6301). It can thus be seen that prepolymers obtained from liquid chloroprene polymers having a hydroxyl functionality of less than 2 do not give good cured products.

Claims (1)

[Scope of Claims] 1. The isocyanate group of the difunctional isocyanate compound is 1.5 to 3.0 with respect to the hydroxyl equivalent of the liquid chloroprene polymer having an average of two or more hydroxyl groups in the molecule and a number average molecular weight of 500 to 10,000. Vulcanization of a liquid polychloroprene-based isocyanate prepolymer obtained by reacting both at a double equivalent ratio with a crosslinking agent in an amount sufficient to react with 0.8 to 1.1 times the equivalent of isocyanate groups in the prepolymer and polychloroprene. A liquid polychloroprene isocyanate prepolymer composition containing an accelerator. 2. The liquid polychloroprene-based polymer is chloroprene or a copolymer obtained by copolymerizing chloroprene and a monomer copolymerizable therewith with acrylate or methacrylate having a hydroxyl group by a radical polymerization method. The liquid polychloroprene-based isocyanate prepolymer composition according to item 1.