JPS6215085B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a method for producing chloroprene with good crystallization resistance at extremely low temperatures of -10°C or lower, and more specifically, 2,3-dichlorobutadiene-1,3 and 2-
When copolymerizing chlorobutadiene-1,3 (hereinafter abbreviated as chloroprene), 2,3-dichlorobutadiene-1,3 is added in portions to disperse and bond into the chloroprene polymer molecular chain.
The present invention relates to a method for producing a chloroprene copolymer with excellent low temperature properties (hereinafter referred to as cryogenic properties) of 10°C to -10°C. Traditionally, the low-temperature properties required of chloroprene elastomers were, at most, delayed crystallization at 0°C and decreased equilibrium crystallization hardness, but in recent years, it has been possible to improve the properties under extremely harsh conditions of -30°C to -10°C. There is a need to improve the low-temperature properties of It is well known that in order to improve the low-temperature properties of chloroprene polymers, it is necessary to interfere with the crystallinity of these polymers, retard the crystallization rate, and reduce the equilibrium hardness. 1)
External plasticization by blending a softener and (2) internal plasticization by copolymerization with other monomers are known. In the case of (1), the cold resistance is improved by adding a softener, but at the same time the mechanical properties are deteriorated. In the case of (2), in addition to chloroprene as a monomer,
2, with one or two monomers selected from 2,3-dichlorobutadiene-1,3, styrene, acrylic ester, methacrylic ester, 1-chlorobutadiene-1,3, and butadiene-1,3.
It is known that a chloroprene copolymer with good low-temperature properties at around 0°C can be produced by component or three-component copolymerization. However, the improvement of cryogenic properties that is the objective of the present invention cannot be achieved by known copolymerization methods, and it is necessary to increase the amount of copolymerization components that act as crystallinity inhibiting factors. In the human body, styrene, acrylic ester, and methacrylic ester have extremely low copolymerization reactivity with chloroprene, and even if the amount of polymerization is increased, the amount contained in the chloroprene copolymer is small, and at the end of polymerization, The amount of remaining monomer increases, which is extremely irrational. Butadiene-1,3 has relatively good copolymerization reactivity, but
Because of its low boiling point, most current methods for producing polychloroprene are based on the atmospheric pressure emulsion polymerization process, and it has the disadvantage of being difficult to adapt to such processes. 2,3-Dichlorobutadiene-1,3 has high copolymerization reactivity with chloroprene. Value (Poly
-mer Handbook second edition), k ₁₁ /k ₁₂ = 0.559, k ₂₂ /k ₂₁ = 1.448, and as the amount of 2,3-dichlorobutadiene-1,3 added increases, the chloroprene copolymer Inside 2,
The 3-dichlorobutadiene-1,3 units tend to bond consecutively. (RCTVol.50, 272~
1977) Therefore, 2,3-dichlorobutadiene-
Simply increasing the amount of 1 and 3 added will result in 2 and 3
-Dichlorobutadiene-1,3 is locally contained in the chloroprene copolymer, and not only does it not act effectively as a crystallinity inhibiting factor, but also 2,3-dichlorobutadiene, which is originally highly crystalline and plastic-like. The properties of a 1,3 polymer are imparted to the chloroprene copolymer, and the cryogenic properties are improved. Reaction (i) ~A・+Ak ₁₁ ~A-A・ Reaction (ii) ~A・+Bk ₁₂ ~A-B・ Reaction (iii) ~B・+Ak ₂₁ ~B−A・ Reaction (iv) ~B・+Bk ₂₂ ~B-B・ ~A・;Growing polymer radical with growing terminal being chloroprene ~B・;Growing polymer radical with growing terminal being 2,
3-dichlorobutadiene-1,3 A; chloroprene monomer _B ; 2,3-dichlorobutadiene-1,3 k ₁₁ ; reaction rate constant k ₁₂ of reaction (i); )'s 〃 k ₂₂ ; 〃 (iv)〃 The present inventors have addressed these problems regarding the production of chloroprene elastomers with good cryogenic properties.
As a result of extensive studies, we found that in a method of copolymerizing 5 parts by weight or more and 25 parts by weight or less of 2,3-dichlorobutadiene-1,3 with more than 75 parts by weight and less than 95 parts by weight of chloroprene monomer, It has been found that a chloroprene copolymer with good cryogenic properties can be obtained by adding 2,3-dichlorobutadiene-1,3 in portions. That is, the feature of the present invention is that when copolymerizing chloroprene and 2,3-dichlorobutadiene-1,3,
By adding 2,3-dichlorobutadiene-1,3 in portions, 2,3-dichlorobutadiene-
2,3-dichlorobutadiene-1,3, which is highly crystalline by uniformly dispersing 1,3 in polymer molecules.
The purpose of the present invention is to produce a chloroprene copolymer which can significantly slow down the crystallization rate at extremely low temperatures and has an extremely low equilibrium crystallization hardness without imparting these properties to the produced copolymer. According to the invention, the weight percent of 1-chlorobutadiene-1,3 contained in the chloroprene monomer is less than 1%, preferably less than 0.5%. 1-Chlorobutadiene-1,3 is produced as an impurity in the chloroprene monomer synthesis process using the so-called acetylene method or the butadiene method, and it is difficult to completely suppress its production. 1-Chlorobutadiene-1,3 is added to the polymer structure with 1,4-
When combined, it assumes a structure with active chlorine, which is believed to have a significant adverse effect on heat aging properties. Other modes of bonding also provide structures with disadvantageous heat aging properties. Therefore,
The smaller the amount of 1-chlorobutadiene-1,3 contained in the chloroprene monomer, the better the result, but since the polymerization activity of 1-chlorobutadiene-1,3 is lower than that of chloroprene, as a practical matter, 1-chlorobutadiene-1,3 is less active than chloroprene. The amount of chlorobutadiene-1,3 is 1
%, it will not have an adverse effect on the chloroprene copolymer of the present application. The amount of chloroprene added exceeds 75 parts by weight.
The amount is less than 95 parts by weight, and the number of parts by weight of 2,3-dichlorobutadiene-1,3 is defined as 5 parts by weight or more and 25 parts by weight or less. If 2,3-dichlorobutadiene-1,3 is less than 5 parts by weight, the effect of inhibiting crystallinity at cryogenic temperatures cannot be exhibited, and if it is more than 25 parts by weight, highly crystalline 2,3-dichlorobutadiene-1,3 The properties of a 1,3 polymer are imparted, and the low temperature properties are rather deteriorated. As a method for adding 2,3-dichlorobutadiene-1,3 in portions, more than 20% by weight and less than 60% by weight of the total amount of 2,3-dichlorobutadiene-1,3 added is present at the start of polymerization, and chloroprene is When the conversion rate exceeds 15% and at least 10% before the conversion rate at which polymerization is stopped, the unadded portion, i.e., the remaining 2.
It is necessary to add 3-dichlorobutadiene-1,3 in portions, with each addition amounting to 40% by weight or less of the total amount added. If the above regulations are violated, 2,3-dichlorobutadiene contained in the chloroprene copolymer produced at the initial stage of polymerization, during the partial addition of 2,3-dichlorobutadiene-1,3, and at the late stage of polymerization.
The amounts of 1 and 3 are different, and furthermore, 2,3-dichlorobutadiene-1,3 in the chloroprene copolymer is continuously bonded, making it impossible to obtain the chloroprene copolymer targeted by the present invention. There is no particular limit to the number of times of divided addition. The polymerization temperature is 20°C or higher, preferably 20 to 60°C, more preferably 40 to 50°C. At temperatures below 20°C, no matter how much copolymerization of 2,3-dichlorobutadiene-1,3 inhibits crystallinity, the bonding mode of chloroprene is 1,4.
-Trans bonds increase, crystallinity increases, and the cryogenic properties of the obtained chloroprene copolymer are difficult to improve. If the temperature exceeds 60°C, the temperature exceeds the boiling point of chloroprene, making it difficult to adapt to the atmospheric pressure emulsion polymerization process that accounts for most polychloroprene production methods. An example that discloses manufacturing conditions similar to those of the present invention is Japanese Patent Publication No. 46-7271. However, this and the present application are completely different in purpose, structure, and effect. In other words, in Special Publication No. 7271, 1971, copies 1 to 30 of 1-
A monomer mixture consisting of chlorobutadiene-1,3 and 1 to 30 parts of butadiene-1,3 or 2,3-dichlorobutadiene-1,3 and 100 parts of chloroprene is polymerized, but 2,3-dichlorobutadiene- Even if 1 to 30 parts of 1,3 are added at once, the low temperature properties at 0°C may be improved, but the cryogenic properties cannot be improved. In addition, special public service
In No. 7271, butadiene-1,3 and 2,3-
There is no suggestion whatsoever regarding the difference in polymerization activity of dichlorobutadiene or the correlation between the copolymerization composition in the polymer structure and low-temperature properties. Next, comparative examples and examples of the present invention will be shown in order to make the present invention easier to understand. Parts and percentages are expressed on a weight basis. Examples 1 to 5 Polymerization was carried out in a stainless steel polymerization can with an internal volume of 30 mm. That is, in a nitrogen stream, 150 parts of water, 3 parts of disproportionated rosin acid soap as an emulsifier, 0.5 part of formaldehyde-sodium naphthalene sulfonate condensate as a dispersant, and 0.8 part of caustic soda as other polymerization aids were charged, and then stirred. Meanwhile, the monomer mixture listed in Table 1 was added together with n-dodecyl mercaptan. Polymerization was carried out under the conditions listed in Table 1, and the conversion rate was
After reaching 70%, para-tertiary butylcatechol and thiodiphenylamine were added to stop the polymerization. Unreacted monomers were removed by steam stripping, and the dried polymer was isolated from the resulting latex by a conventional freeze-coagulation method. Product properties are listed in Table 2. Comparative Examples 1 to 7 Dry polymers were isolated using the same formulations as shown in Examples using the monomer compositions and polymerization conditions listed in Table 1. Product properties are listed in Table 2. In both Examples and Comparative Examples, the following formulations were vulcanized and the physical properties were measured. Blend Polymer 100 parts Phenyl α-naphthylamine 1 Magnesia 4 SRF carbon black 50 Rapeseed oil 20 Zinc white 5 2-mercaptoimidazoline 0.35 Vulcanization Press vulcanization at 150℃ for 30 minutes

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Claims (1)

[Claims] 1 The content of 1-chlorobutadiene-1,3 is
2-chlorobutadiene less than 1.0% by weight
More than 75 parts by weight and less than 95 parts by weight of 1, 3 and 2, 3-
Dichlorobutadiene-25 with 5 parts by weight or more of 1,3
In the method of copolymerizing less than parts by weight, 2,3-
More than 20% by weight and not more than 60% by weight of the total amount of dichlorobutadiene-1,3 added at the start of polymerization,
When the conversion rate of 2-chlorobutadiene-1,3 exceeds 15% and is at least 10% before the conversion rate at which polymerization is stopped, 2,3-dichlorobutadiene-1,
A method for producing a chloroprene copolymer, characterized in that the unadded portion of 3 is added in portions so as to be 40% by weight or less of the total addition amount per addition, and polymerized at a polymerization temperature of 20° C. or higher. 2. The method for producing a chloroprene copolymer according to claim 1, wherein the polymerization temperature is 20 to 60°C.