JPH0421693B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is an epoxy resin curing agent made of a polysulfide polymer. In particular, when an epoxy resin is cured with an amine curing aid, the curing speed is increased by coexisting with the amine curing aid, and a cured product with excellent physical properties can be obtained. The present invention relates to an epoxy resin curing agent made of a polysulfide polymer. Currently, liquid polysulfide polymers are widely used as modifying agents for epoxy resins. This liquid polysulfide is copolymerized by the addition reaction of the thiol group, which is the terminal structure of the molecule, with the epoxy group in the epoxy resin, resulting in impact resistance,
Provides a cured product with excellent flexibility, chemical resistance, electrical properties, etc. at low temperatures. However, although the curing reaction by copolymerization of epoxy resin and liquid polysulfide is accelerated by amines, the curing speed generally takes several hours. The present inventors have repeatedly studied and produced a liquid polysulfide polymer that has not only the above-mentioned properties as a modifying agent for epoxy resins that have been conventionally used, but also maintains remarkable fast curing properties. succeeded in. The curing speed when using the epoxy resin curing agent made of the liquid polysulfide polymer of the present invention is as follows:
Average molecular weight 1000, thiol content 6.5wt%, which has been most commonly used as a modification agent for epoxy resins.
This is about 10 times faster than liquid polysulfide with a degree of crosslinking of 2 mol%. Furthermore, the strength of the cured product after curing was developed faster than that of the liquid polysulfide. The liquid polysulfide polymer for the epoxy resin curing agent of the present invention has the general formula R'(X)n...() {wherein R' is an aliphatic or aromatic hydrocarbon group (containing an ether bond) or may be substituted with a hydroxyl group), n is 3 or 4, and x is a halogen atom. } and ^a polyfunctional alkyl halide represented by ^the general formula and x is a halogen atom.)
A copolymer obtained by reacting a mixture of difunctional alkyl halides represented by with an alkali polysulfide, in which the polyfunctional monomer during polymerization accounts for 20 mol% or more and 60 mol% or less of the total monomers, It is a polysulfide polymer that contains a thiol group and is liquid at room temperature. The tri- or tetra-functional monomer represented by the general formula serves as a crosslinking point in the polymer, which allows the cured product to develop strength quickly, as well as strengthens the thiol group that is the molecular terminal structure of the polymer. In order to increase the content, the curing speed is increased. In addition, the bifunctional monomer represented by the general formula serves as the main skeleton that connects the crosslinking points, and also has the effect of accelerating the curing of other curing agents containing hydroxyl groups, amino groups, etc. It is necessary as a convenient monomer to introduce functional groups with That is, the polysulfide polymer for the epoxy resin curing agent of the present invention has (A) general formula A or B S _X/2 S _X/2 R ¹ S _{X/2 X/2} (A), S _X/2 S _{X/ 2} R 1 S ^X / _{2 S} ) and (B) ^the general formula S _X/2 ^R ₂ S It is a hydrocarbon group, and contains at least one type of both repeating units represented by 1<x<5. The proportion thereof is 20 mol% or more and 60 mol% or less. In addition, this polymer is characterized by containing polysulfide bonds in the molecular chain and thiol groups as a molecular terminal structure, and having an average molecular weight of 300 to 10,000, and a liquid having a viscosity of 0.1 to 5,000 poise at 25°C. shall be. R' in the general formula is a trivalent or tetravalent aliphatic or aromatic hydrocarbon group (containing an ether bond, or or may be substituted with a hydroxyl group), for example, CH ₃ CH ₂ C (CH ₂ OCH ₂ OCH ₂ CH ₂ −) ₃ , CH ₃ C (CH ₂ OCH ₂ OCH ₂ CH ₂ −) ₃ , etc. can be mentioned. These repeating units (A) are bonded to adjacent repeating units through 3 or 4 polysulfide bonds, thus forming crosslinking points in the polymer, allowing the cured product to develop strength quickly. In addition, it increases the content of thiol groups, which are the terminal structure of the molecule, and speeds up the curing rate, and is essential as the most essential component of this polymer. The proportion of repeating unit (A) in all repeating units, that is, the degree of crosslinking {number of moles of A/(number of moles of A + number of moles of B) ×
100, mol%} is suitably 20 or more and 60 or less. The degree of crosslinking greatly affects the performance of the present polymer as an epoxy resin curing agent, particularly the curing speed and strength of the cured product. If the degree of crosslinking is small, the curing speed or time required to develop strength will be longer, that is, the quick curing property will be poor. When the degree of crosslinking is 20 mol% or less, there is no significant difference from the existing liquid polysulfide having an average molecular weight of 1000, a thiol content of 6.5 wt%, and a degree of crosslinking of 2 mol%. On the other hand, when the degree of crosslinking exceeds 60 mol%,
Problems in production such as increase in raw materials required for production, selection of reaction conditions, deterioration of color tone and odor due to increase in by-products are increasing, and it is difficult to reproduce the desired product to a commercially viable level. This makes it difficult to manufacture with good performance. R ² in the general formula is a divalent aliphatic or aromatic hydrocarbon group that can be chain-bonded to adjacent repeating units through two polysulfide bonds (even if it contains an ether bond or is substituted with a hydroxyl group) For example, (-CH ₂ )-n n=1~10, (-CH ₂ CH ₂ O)-nCH ₂ CH ₂ - n=1~
100,

[Formula] n=1 to 100, −CH ₂ CH ₂ OCH ₂ OCH ₂ CH ₂ −,

【formula】

【formula】

[Formula] −CH ₂ CH ₂ CH ₂ OCH ₂ CH ₂ CH ₂ −, −CH ₂ CH ₂ CH 2 CH ₂ OCH ₂ CH ₂ CH ₂ CH ₂ −, −CH ₂ CH ₂ CH ₂ OCH _{2 OCH 2} CH ₂ CH ₂ −, −CH ₂ CH ₂ CH ₂ CH ₂ OCH ₂ OCH ₂ CH ₂ CH ₂ CH ₂
−、

[Formula] −CH ₂ CH=CH−, −CH ₂ CH=CHCH ₂ −,

[Formula] (CH ₃ ) ₂ C(CH ₂ −) ₂ ,

【formula】 【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

[Formula] etc. These repeating units (B) are (A)
It is a carrier that connects the crosslinking points formed in a chain, and gives flexibility to the cured product, and is used to introduce functional groups that have a curing accelerating effect, such as hydroxyl groups and amino groups, into the skeleton. It is convenient as The general formula and x in it mean the average number of sulfur atoms constituting the polysulfide bonds contained in this polymer, that is, the sulfur rank as known by those skilled in the art, and is generally used when producing polysulfide. It is determined by the composition of the raw material alkali polysulfide. x can be any numerical value in the range of 1<x<5, but is usually about 2. The average molecular weight of the present polymer can be freely adjusted in one step in the production method of this polymer, and has a large effect on the viscosity of the polymer and the content of thiol groups, which are terminal structures. The average molecular weight range is 300 or more and 10,000 or less, the viscosity of the polymer corresponding to this range is 0.1 poise or more and 5000 poise or less (at 25°C), and the thiol group content is 3% by weight or more and 30% by weight. It is about the following. In view of compatibility and workability as an epoxy resin curing agent, the viscosity is more preferably 1 poise or more and 1000 poise or less, and the thiol group content is 5% by weight or more and 20% by weight or less. Also, these ranges have an average molecular weight of 450 or more.
This corresponds to about 7000 or less of this polymer. Among the prior art related to polysulfides, a detailed description of the method for producing rubbery polysulfides can be found in U.S. Pat. A method for producing polysulfide polymers is described. Further, a detailed description of the method for producing liquid polysulfide can be found in US Pat. No. 2,466,963. The manufacturing method is to treat a latex of rubbery polysulfide with a system that combines a nucleophile and a reducing agent to form a liquid polysulfide with a relatively low molecular weight. Among these prior art, U.S. Patent No. 2,363,614
In this issue, there is also an example of producing a solid rubber-like polysulfide with a degree of cross-linking of 100 mol%, but the U.S. Patent No.
All of the liquid polysulfides whose production methods are described in No. 2466963 have a degree of crosslinking of 4 mol% or less, and liquid polysulfide with a degree of crosslinking as high as this polymer has never been produced. The present inventors improved the method for producing liquid polysulfide polymers that has been most commonly used in the past, and succeeded in producing highly crosslinked liquid polysulfide polymers. This polymer can be produced through three steps: polymerization, liquefaction, and post-treatment, similar to existing low-crosslinked liquid polysulfides. Polymerization refers to the process of reacting an organic halogen compound, which is a raw material for this polymer, with an alkali polysulfide to produce a latex, which is an intermediate. , which has a large effect on odor, etc. The reaction is usually in the presence of an emulsifier
It is carried out for several hours at temperatures between 60 and 130 degrees Celsius. Liquefaction refers to treating the latex obtained in the polymerization process with a system that combines a nucleophilic reagent such as sodium bisulfide and a reducing agent such as sodium sulfite to reduce the molecular weight, and then converting the latex into particles by removing the emulsifier. This refers to the process of destroying the polymer and producing a liquid polymer, and it has a large effect on the molecular weight, thiol group content, viscosity, etc. of the target polymer. The amount of raw materials and reaction conditions used in the liquefaction process vary depending on the expected viscosity of the target polymer, but usually 0.8 to 3.5 moles of reducing agent and 0.5 mole of reducing agent per mole of thiol group of the target polymer. ~1.4 moles of nucleophile, 0.8 to 3.5 moles of neutralizing acid, 60 to
It is carried out at a temperature of 100°C for about 0.5 to 2 hours. Post-treatment refers to water contained in the crude polymer obtained in the liquefaction process, sludge mixed in during each process,
This is a process to remove inorganic salts, etc., and has a large effect on the stability, color tone, etc. of the target polymer. Operations include centrifugation, washing, drying, and filtration. The present inventors have reproduced a highly crosslinked liquid polysulfide polymer that has good performance in terms of viscosity, color tone, odor, storage stability, curing speed when mixed with epoxy resin, physical properties of cured product, etc. using the above manufacturing method. We succeeded in manufacturing it efficiently. This polymer is soluble in any proportion with bisphenol A-based epoxy resin prepolymers and amines such as 2,4,6-tris(dimethylaminomethyl)phenol, and is also soluble in benzene, toluene,
Soluble in chloroform, ethyl acetate,
It became emulsified in acetone and was insoluble in water and n-hexane. In addition to being used as an epoxy resin curing agent, this polymer can also be used as a fast-curing aid when curing epoxy resins with amine-based curing agents, etc., and as a modification agent that improves impact resistance, low-temperature flexibility, chemical resistance, etc. It can be used as Examples of the present invention are shown below. Example 1 (Polymerization) A 2.4 mol aqueous sodium polysulfide solution was charged into a reactor equipped with a stirrer, a thermometer, and a dropping funnel, and maintained at 80°C in an oil bath. While stirring, a small amount of sodium alkylsulfonate was added followed by 0.2 mol of magnesium chloride in water. After stirring for 10 minutes, bis(2chloroethoxy)methane (1.2 mol) and 1,2,3
- A mixture of tribromopropane (0.8 mol) was added dropwise. After the monomer was added dropwise over about 1 hour, the temperature of the reaction system was raised and stirring was continued at 100°C for 3 hours. As the reaction progressed, a yellow-white latex was precipitated. By leaving the reaction system at room temperature overnight,
The mixture was separated into two layers, a latex layer and a supernatant liquid, at a volume ratio of about 1:1. (Liquefaction) After discarding the supernatant liquid by decantation, the latex layer was transferred to a reactor equipped with a stirring device, a thermometer, and a dropping funnel, and after adding 3.6 mol of sodium sulfite, the mixture was heated and heated. When the temperature of the reaction system rose, 1.25 mol of sodium hydrogen sulfide was added and the reaction was continued for 1 hour. After neutralizing the reaction with 0.1N diluted hydrochloric acid, stirring was continued for an additional 30 minutes. The reaction system was then allowed to stand at room temperature for 1 hour, and the reaction system was separated into a portion containing approximately 500 ml of polymer and a supernatant liquid. (Post-treatment) After discarding the supernatant liquid by decantation, the polymer portion was centrifuged to remove sludge and the like. The obtained crude polymer was washed and then dried using a rotary evaporator. Moisture content 0.3
By reducing the amount to below % by weight and filtering, 230 g of a transparent reddish-brown target product was obtained. This is called sample A. Comparative Example 1 Sample B was obtained in the same manner as in Example 1 except for the following differences. Bis(2-chloroethoxy)methane 1.8 mol 1,2,3-tribromopropane 0.2 mol Example 2 Sample C was obtained in the same manner as in Example 1 except for the following differences. Bis(2-chloroethoxy)methane 0.8 mol 1,2,3-tribromopropane 1.2 mol Example 3 (Polymerization) A 501 reactor equipped with a stirrer, thermometer, and dropping funnel was used in Example 1. Polymerization was carried out in the same manner as in Example 1, except that 25 times the amount of each raw material was used. (Liquefaction, post-treatment) Liquefaction,
After post-treatment, a polymer having a viscosity of 8 poise at 25°C was obtained. The remaining half of the latex was similarly liquefied and post-treated to obtain a polymer having a viscosity of 10 poise at 25°C. This polymer was heated and mixed with the previous 8 poise polymer to obtain 5.3 kg of the desired product. This is called sample D. Example 4 A polymer having a hydroxyl group in the side chain was obtained in the same manner as in Example 1 except that the following compound was used as a monomer. This is called sample E. Sodium polysulfide aqueous solution 2.25 mol Bis(2-chloroethoxy)methane 1.3 mol Trimethylolpropane tris(2-chloroethyl formal) 0.5 mol Epichlorohydrin 0.2 mol Example 5 Polymer was added to a reactor equipped with a stirrer, thermometer, and dropping funnel. 0.36 mol of sodium sulfide and sodium bisulfide
1.68 mol and 300 ml of water were charged, heated and stirred in an oil bath, and completely dissolved. After adding a small amount of surfactant and magnesium chloride and stirring for 10 minutes, 0.6 moles of bis(2-chloroethoxy)
A mixture of methane and 0.4 mol of 1,2,3-tribromopropane was added dropwise. After raising the temperature of the reaction system, it was stirred for 5 hours and left to stand at room temperature, and a viscous polymer precipitated. This polymer is thoroughly washed and dried in a rotary evaporator to obtain the desired polymer.
Got 129g. This is called sample F. Example 6 As samples A to F and a comparative example, screws (2
-Average molecular weight produced using chloroethoxy)methane and 1,2,3-tribromopropane as raw materials
1000, a liquid polysulfide with a thiol content of 6.5 wt% and a degree of crosslinking of 2 mol% (this is referred to as sample G), an average molecular weight of 1600, and a thiol content of 4.1 wt, manufactured using bis(2-chloroethoxy)methane and epichlorohydrin as raw materials. %, properties of a total of eight samples of non-crosslinked liquid polysulfide having hydroxyl groups in side chains (this is referred to as sample H) are shown in Table 1. Note that the thiol group content in the table was measured by iodometric titration. In addition, the curing speed was calculated using 1.0 g of epoxy resin (Epicote 828) and 0.1 g of curing catalyst for 1.0 g of each sample.
4,6-Tris(dimethylaminomethyl)phenol} was mixed at 20°C, and the time until it hardened in a thin film state was measured. Further, the maximum tensile stress of the cured product was measured at a displacement rate of 5 mm/min after curing a dumbbell-shaped test piece of the same ratio mixture at 20° C. for a predetermined time.

【table】

Claims (1)

[Claims] 1 (A) General formula A or B S _X/2 S _X/2 R ¹ S _X/ 2 _X/2 ... (A) S _X/2 S _X/2 R ¹ S _{X/ 2 S} ^_ Represented repeating unit, ^and (B) general formula S _X/2 ^R ₂ S group, and 1<x<5.) containing at least one type of both repeating units,
The proportion of the number of moles of (A) in the total number of moles of (A) and (B) is 20 mol% or more and 60 mol% or less, and 3
An epoxy resin curing agent comprising a liquid polysulfide polymer containing terminal thiol groups in an amount of not less than 30% by weight and a viscosity of not less than 0.1 poise and not more than 5000 poise at 25°C.