JPS61238808A - Modifier for producing chloroprene rubber and production of chloroprene rubber by using same - Google Patents

Abstract

PURPOSE:To obtain chloroprene rubber which, when vulcanized, needs no vulcanization accelerator and is excellent in heat aging resistance, by emulsion- polymerizing a chloroprene monomer in water in the presence of a specified polysulfide polymer and peptizing the polymer. CONSTITUTION:A modifier for the production of chloroprene rubber comprising a polysulfide polymer of formula I (wherein x is 4-6, n<=150, R is formula II and m is 2-5) is produced by, for example, a process in which a dimercaptan is reacted with a sulfur chloride. 100pts.wt. chloroprene or its mixture with a copolymizable monomer (e.g., butadiene) is emulsion-polymerized in water in the presence of 1.5-10pts.wt. above modifier and the obtained polymer is peptized to obtain the purpose chloroprene rubber. this rubber can be vulcanized without using any vulcanization accelerator such as ethyleneurea having a problem of carcinogenicity.

Description

[Detailed Description of the Invention] C. Industrial Application Field] This invention relates to a novel modifier that can be used in the production of chloroprene rubber, and a method for producing chloroprene rubber modified with it and having excellent heat resistance. .

[Conventional technology]

Currently, chloroprene rubber (hereinafter referred to as OR) is used as a special general-purpose rubber that has excellent rubber elasticity and is well-balanced in heat aging resistance, ozone resistance, and oil resistance.
It is widely used in various industrial and automobile parts such as tubes, gaskets, joint boots, and packing, as well as sponges and adhesives.

Currently commercially available ORs are broadly classified into sulfur-modified ORs and non-sulfur-modified ORs, depending on the modifier used during production.

The former is obtained by peptizing a gel-like chlorotetraprene/sulfur copolymer obtained by polymerizing monocapsular chloroprene in the presence of sulfur with a peptizing agent such as a tetraalkylthiuram compound; n-dode? Sulfur-modified OR and non-sulfur-modified OR, which are obtained by polymerizing p-proprene monomer using a mercaptan compound such as lumercabutan as a molecular weight modifier, each have their own characteristics and can be used for appropriate purposes. However, each has its drawbacks. Non-sulfur-modified OR has superior heat resistance and compression set compared to sulfur-modified OR, but it is difficult to obtain vulcanized rubber with superior physical properties unless ethylene thiourea is used as a vulcanization accelerator. I can't come. Ethylene thiourea is an excellent vulcanization accelerator for non-sulfur-modified ORK, but its carcinogenicity has become a problem in recent years, and its use is expected to be restricted in the future. . Several researches have been made to develop non-sulfur-modified OR vulcanization accelerators to replace ethylene thiourea, but to date no vulcanization accelerator comparable to ethylene thiourea has been found.

On the other hand, sulfur-modified OR, unlike non-sulfur-modified OR, can be vulcanized only with a metal oxide without using ethylene thiourea, and a vulcanized rubber with high mechanical strength can be obtained. However, due to the polysulfide bonds present in the molecular chain, heat aging resistance and compression set are reduced due to non-sulfur-modified O.
Extremely inferior to R.

Under these circumstances, several ORs with properties intermediate between conventional non-sulfur-modified ORs and sulfur-modified ORs are on the market, but the vulcanization characteristics and physical properties of vulcanized rubber are still not satisfactory. It's not a kimono.

[Problem that the invention seeks to solve]

The present invention was completed as a result of intensive research to solve these problems.

That is, the present invention provides a new modifier for producing gastric chloroprene rubber and a chloroprene rubber that can be vulcanized without using a vulcanization accelerator like sulfur-modified OR and has heat aging resistance equivalent to or better than that of non-sulfur-modified rubber. The purpose is to provide a manufacturing method.

[Means for solving problems]

The present invention provides a modifier for producing chloroprene rubber represented by the following formula [1], -(-R-8!-)-(1) [where X is an integer of 4 to 6, n is an integer of 150 or less, R
-(CH2-014o4 o total o%, !II is 2
It is an integer of ~5. ] and in the presence of 1.5 to 10 parts by weight of the modifier based on 100 parts by weight of the total monomers. (B) [hereinafter (4)
) or (B) is referred to as a chloroprene monomer] is subjected to aqueous emulsion polymerization, followed by peptization.

The modifier of the present invention has an average degree of polymerization (n
) is 150 or less polysulfide polymer. Similar polysulfide polymers include natural rubber, isoprene rubber, and butadiene rubber.

It is already known that it can be used as a vulcanizing agent for synthetic rubbers such as chloroprene rubber, nitrile rubber, and ethylene propylene rubber. (For example, JP-A-57-170959)
However, it was completely unknown that a specific polysulfide polymer could be used as a modifier in the process of producing chloroprene rubber to produce a chloroprene-based polymer for normal use.

Polysulfide polymers with an average degree of polymerization exceeding 150 are difficult to mix sufficiently with chloroprene monomers, making it impossible to obtain polymerized products with stable properties or, in some cases, making polymerization impossible, and they are used as modifiers. It is not possible.

The modifier of the present invention can be obtained, for example, by reacting dimercaptan and sulfur chloride as shown in the following formula [2].

II 1) g-R-8H+1) Sx a 1t-+-
(-R-1i1)-)v→2pHO1(2) [Here, y is an integer from 2 to 4, R is -(OH! OHOH1-0)
〇Ht-OHt-CH2-CH2-, m is an integer of 2 to 5, and p is an integer of 150 or less. ] Polysulfide poly! represented by the following formula [1] A method for producing rotaprene rubber by aqueous emulsion polymerization using - as a modifier will be explained.

As the monomer, chloroprene can be used alone or in combination with chloroprene and a monomer copolymerizable with chloroprene for the purpose of improving the crystallization resistance of the produced chloroprene rubber. There are no particular restrictions on the monomers that can be copolymerized, but examples include butadiene, isoprene, 1-p-butadiene-1,3,2,5-dichloro-butadiene-1,5, styrene, acrylate , methacrylonitrile, methacrylic esters such as methyl methacrylate, and acrylic esters such as methyl acrylate. These monomers are used alone or as a mixture of two or more monomers for copolymerization with chloroprene. The amount of monomer copolymerized with chloroprene is
It is usually 50 parts by weight or less per 100 parts by weight of the total monomers.

In the present invention, the polysulfide polymer is used in an amount of 5 to 10 parts by weight, preferably 5 to 6 parts by weight, per 100 parts by weight of the tetraloprene monomer.

If the amount of the polysulfide polymer is too small, it will be impossible to reduce the viscosity to a level that can be used in the peptizing step described below, and if it is too large, the polymerization rate will be extremely slow, resulting in poor productivity.

As described above, the noprene monomer and the polysulfide polymer are stirred together with an aqueous emulsifier solution to form an emulsion and subjected to polymerization. As the emulsifier, known emulsifiers that are commonly used in the production of plain rubber can be used. Generally speaking
Alkali metal salts of gastric acid such as zinc acid, Wood's acid, tall oil rosin acid, and disproportionated 9-polymerized rosin acid are used, but in addition to these, higher fatty acids or naphthalenesulfonic acid and formaldehyde are used. There is no problem in using an anionic surfactant such as an alkali metal salt of a condensate of , and/or a nonionic surfactant such as polyethylene glycol nonyl 7-ether.

After the chloroprene monomer and polysulfide polymer emulsion reach a predetermined temperature, a polymerization initiator is added to initiate polymerization. Polymerization at 0-70°C, preferably 10-50°C
temperature, 7-15f) pH. Potassium persulfate is used as a polymerization initiator.

Known inorganic or organic peroxides such as ammonium persulfate, hydrogen peroxide, and di-t@rt-butyl peroxide are used. Polymerization is usually carried out by adding a known polymerization inhibitor such as thiodiphenylamine, t@rt-butylcatechol, or a water-soluble salt of dialkylthiocarbamic acid to the polymer when the conversion rate of the chloroprene monomer reaches 60 to 90%. It is stopped by adding Q in an amount in the range of 01 to 2% by weight.

The chloroprene polymer produced at this point is a benzene-insoluble gel-like glue-on-prene polymer containing one polysulfide polymer unit produced by a chain transfer reaction between polymer radicals and polysulfide polymer during polymerization, and is usually used as is. Since the viscosity is too high to be subjected to processing, it is subjected to a peptization process to lower the viscosity to a level that is easy to process. The gel-like polymer can be reacted with a suitable peptizer capable of cleaving the polysulfide units in the main chain.

As the peptizer used to peptize the gel-like chloroprene-based polymer to form a sol-like polymer, a known peptizer used in the production of sulfur-modified OR can be used. Examples of these include tetraalkylthiuram disulfide compounds such as tetraethylthiuram disulfide and tetrabutylthiuram disulfide, or mercaptans represented by the general formula R'SH or their ionized sulfides.
R'S-M'' (wherein is an alkali cation or ammonium and R' is a chain or branched alkyl group having 2 to 6 carbon atoms, or an alkylaryl group, aryl carbonyl group.

Examples include compounds represented by an alkylcarboxyl group, an alkylnaphthyl or heptyl group, an arylthiazole or thiazole group or its sodium salt, an arylimidazole or imidazole group, or an alkylxanthate group.

Deflocculating agent is usually Q, 1 to 5 times JL for gel polymer.
tf s-% 歇W＾Makurahoji pattern U side is shadow life ri0-
This is carried out at a temperature of 60° C. until a predetermined viscosity is reached.

After the peptization reaction is completed, unreacted monomers are removed from the emulsion by steam distillation, acidified by adding a weak acid, and a sol-like chloroprene polymer is obtained by a conventional freezing-coagulation-drying method. isolate.

〔Effect of the invention〕

The chloroprene polymer obtained in the above manner can be vulcanized without using a vulcanization accelerator such as ethylene thiourea in the same way as sulfur-modified OR, and is surprisingly effective not only in sulfur-modified OR. Especially non-sulfur modified OR
Provides a vulcanized rubber with superior heat aging resistance compared to other materials.

〔Example〕

Synthesis of polysulfide polymer> Synthesis example 1: α in a 1,0OOaj flask equipped with a cooling tube.
A solution of 416 mol of triglycol dimercaptan in dry petroleum ether (1,000 ILt) VC [1416 mol of sulfur monochloride in dry petroleum ether (200 d) is slowly added dropwise with stirring at room temperature.

If the stirring is continued after the dropwise addition is completed, the polysulfide polymer will precipitate in the reaction system as the reaction progresses. After the reaction was carried out for 24 hours, the precipitated product was taken out, dissolved in benzene, and washed repeatedly with water using a separating funnel until the aqueous phase became neutral. After removing benzene using an evaporator, the residue was further dried under reduced pressure using a vacuum pump for 24 hours to obtain a yellow candy-like substance 1)59 (yield 98%). The number average molecular weight of the produced polysulfide polymer measured by gel permeability chromatography (hereinafter abbreviated as GPO) was 700, and the total sulfur content measured by elemental analysis was 67.5% (calculated value 6'16%). . The product was a polysulfide polymer of formula [1], where x = 4, rn = 2, and n = 27.

Synthesis Example 2: A polysulfide polymer was synthesized in the same manner as Synthesis Example 1 except that dry benzene was used instead of dry petroleum ether as the reaction solvent. In this case, no product precipitated into the reaction system. The number average molecular weight measured by the produced polysulfide polymer〇〇POIC is 45.0
00, and the total sulfur content measured by elemental analysis was 6aO% (calculated value 6'16%). The product is x =
4, m = 2, n = 184 polysulfide polymer.

<Examples 1 to 3, Comparative Example 1> 5.0001) Monomers with the formulation shown in Table 1, polysulfide polymer, and an emulsifier aqueous solution with the following formulation were charged into the autoclave of 1) and stirred to form an emulsion. .

Disproportionated potassium rosinate 90 9FMS*
14 Sodium hydroxide 1.5 Trisodium phosphate 22 Distilled water 1800 (*sodium salt of a condensate of 7 talenesulfonic acid and formaldehyde) After the temperature of the emulsion reaches 40°C, add potassium persulfate in a nitrogen atmosphere. Polymerization was carried out by continuously adding an aqueous solution using a pump. When the monomer conversion rate reached 70%, an aqueous solution of dimethylammonium dithiocarvermate was added to stop the polymerization.

Subsequently, 3399 g of peptizer emulsion having the following composition was added and 40 g.
Peptization was carried out at ℃ for 5 hours.

Tetraethylthiuram disulfide 20 parts by weight chloroprene rubber was obtained. The gel fraction, o and Mooney viscosity of the produced chloroprene rubber are shown in Table 1. According to the present invention, it is possible to produce chloroprene rubber containing almost no gel content. (Here, the gel content was measured by the following method.

Approximately 1 chloroprene rubber per 200 mesh Harris basket
After 40 hours of immersion in benzene containing 900 ml of benzene at room temperature, the weight of the chloroprene rubber remaining in the Harris basket was measured, and the ratio of this to the initial weight of chloroprene rubber was determined. ) Comparative Example 2> Polymerization was attempted in the same manner as in Example 1 except that the polysulfide polymer of Synthesis Example 2 was used as a modifier, but the dispersibility of the polysulfide polymer in latex was poor, resulting in lumps and polymerization. It was impossible to do.

Example of physical property measurement Chloroprene rubber produced in Examples 1 and 2.

Skyplane R-22 (manufactured by Toyo Soda Kogyo ■: Sulfur-modified O
R) and Skyprene B-50 (manufactured by Toyo Soda Kogyo ■; non-sulfur modified OR) were roll-kneaded in the formulation shown in the third coating to obtain a compound. These Mooney viscosity, scorch time to 3rd coating% 1/4 meter vulcanization curve (oscillating, disc.

Uses rheometer (manufactured by Monsanto), vibration angle 1°.

Figure 1 shows the temperature of 150°C. The Noritaroprene rubber of the present invention can be vulcanized using only metal oxides without using a vulcanization accelerator.

The results of measuring the physical properties of a vulcanized rubber sheet obtained by press-vulcanizing the above rubber bound at 150° C. for 40 minutes are shown in the third column. It is clear that the vulcanized rubber obtained from the chloroprene rubber of the present invention has superior heat aging resistance not only to sulfur-modified OR but also to non-sulfur-modified OR.

third garment (Unit: □)

[Brief explanation of the drawing]

Figure 1 shows the rheometer vulcanization curve of beam no prene rubber.

Claims (2)

[Claims] (1) A modifier for producing chloroprene rubber represented by the following formula [1]. -(-R-Sx-)_n- [1] [Here, x is an integer of 4 to 6, n is an integer of 150 or less, R
is-(CH_2-CH_2-O)_m-CH_2-CH
_2-, m is an integer from 2 to 5. ] (2) Chloroprene alone or a mixture of chloroprene and monomers copolymerizable with chloroprene to a total monomer concentration of 100%
A method for producing chloroprene rubber, which comprises carrying out aqueous emulsion polymerization in the presence of 1.5 to 10 parts by weight of a polysulfide polymer represented by the following formula [1], followed by peptization. -(-R-Sx-)_n- [1] [Here, x is an integer of 4 to 6, n is an integer of 150 or less, R
is-(CH_2CH_2-O)_m-CH_2-CH_
2-, m is an integer from 2 to 5. ]