JP6854818B2 - Flame-retardant rubber composition, its vulcanized product and molded product - Google Patents

Description

The present invention relates to a flame-retardant rubber composition, a vulcanized product thereof, and a molded product. More specifically, the present invention relates to a flame-retardant rubber composition of chloroprene rubber, a vulcanized product thereof, and a molded product.

Chloroprene rubber is excellent in mechanical strength, heat resistance and oil resistance, and is widely used as a material for industrial rubber parts due to its good balance of physical properties. In addition, chloroprene rubber has a characteristic of being excellent in flame retardancy, and is suitably used in rubber parts of buildings and structures, ships, railways, coal mines, automobile fields, etc., which require flame retardancy. On the other hand, in recent years, the performance required for the rubber parts has been remarkably increased, and in addition to the above-mentioned mechanical strength, heat resistance and oil resistance, outstanding flame retardancy is required.

Therefore, in order to enhance the flame retardancy of the chloroprene rubber composition, the vulcanized product, and the molded product, a method of adding various flame retardants has been conventionally adopted (see, for example, Patent Documents 1 to 3). For example, in Patent Document 1, flame retardancy is achieved by adding a predetermined amount of chlorinated paraffin and antimony trioxide to chloroprene rubber.

Further, in Patent Documents 2 and 3, flame retardancy is improved by adding a predetermined amount of red phosphorus or a silane coupling agent together with an excess amount of metal hydrate such as magnesium hydroxide to chloroprene rubber.

Japanese Unexamined Patent Publication No. 2011-127047 Japanese Unexamined Patent Publication No. 2005-146256 JP-A-2007-23102

However, in the methods described in Patent Documents 1 to 3 described above, a method of adding a plastic flame retardant together or adding an excessive amount of a specific flame retardant is adopted, so that the mechanical strength of the vulcanized rubber is lowered. It was difficult to balance flame retardancy and mechanical strength. Therefore, in order to obtain an industrial rubber part having excellent flame retardancy, mechanical strength is sacrificed, which inevitably limits the technical application range.

Therefore, an object of the present invention is to provide a rubber composition, a vulcanized product thereof, and a molded product capable of obtaining a vulcanized product having excellent flame retardancy without lowering the mechanical strength.

The flame-retardant rubber composition according to the present invention is based on 100 parts by mass of chloroprene rubber.
(A) represented by the following chemical formula (1), hydrotalcite compound BET specific surface area measured by a one-point method specified in JIS Z8830 is ^{_{3~50m 2 / g M x Al y}} (OH) z CO ₃ · _mH 2 O (1)
(In the formula, M is a divalent metal ion consisting of at least one of Mg or Zn, x is 3 to 7, y is 1 to 3, z is 7 to 20, and m is a coefficient value in the range of 2 to 7. Shown), 4 to 16 parts by mass,
(B) Aluminum hydroxide having a central particle size of 0.5 to 5.0 μm obtained by the laser diffraction method described in JIS Z 8825 was added to 10 to 80 parts by mass.
Contains. JIS is an abbreviation for Japanese Industrial Standards.
In this rubber composition, the extraction amount (hereinafter, also referred to as “ETA”) of the ethanol / toluene azeotropic mixture (mixture of 70 volumes of ethanol and 30 volumes of toluene, hereinafter also referred to as “ETA”) specified in JIS K 6229 as the chloroprene rubber. A chloroprene rubber having an (also referred to as "ETA extraction amount") of 3.0 to 9.0% by mass can be used.
Further, 2 to 16 parts by mass of a bromine-containing organic compound having a bromine content of 60 to 85% per 100 parts by mass of the chloroprene rubber may be contained.

The vulcanized product according to the present invention is a vulcanized product of the above-mentioned flame-retardant rubber composition.
Further, the molded product according to the present invention is made of the above-mentioned vulcanized product.

According to the present invention, since a specific amount of a specific aluminum hydroxide is blended with a specific hydrotalcite compound in the chloroprene rubber, the flame retardancy of the vulcanized product can be improved without lowering the mechanical strength. It can be dramatically improved.

Hereinafter, suitable embodiments for carrying out the present invention will be described. It should be noted that the embodiments described below show an example of typical embodiments of the present invention, and the scope of the present invention is not narrowly interpreted by this.

<Rubber composition>
The flame-retardant rubber composition of the present embodiment contains a specific hydrotalcite compound and aluminum hydroxide. Further, the rubber composition of the present embodiment may also contain commonly used flame retardants, antiaging agents, carbon blacks, softeners, fillers and the like as long as the mechanical strength is not lowered. Hereinafter, each component will be described in detail.

[Chloroprene rubber]
The chloroprene rubber described in the present invention is obtained by polymerizing a raw material monomer containing chloroprene as a main component and then washing and drying as necessary, and is a chloroprene homopolymer or chloroprene which is a product of a polymerization reaction. In addition to the copolymer of and other monomers, an emulsifier, a dispersant, a catalyst, a catalyst activator, a chain transfer agent, a polymerization inhibitor, etc. added at the time of polymerization may be contained.

Examples of the monomer copolymerizable with chloroprene include acrylic acid esters such as methyl acrylate, butyl acrylate and 2-ethylhexyl acrylate, and methacrylic acid such as methyl methacrylate, butyl methacrylate and 2-ethylhexyl methacrylate. Acid esters, hydroxy (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxymethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate, and 2,3-dichloro-1,3- Examples thereof include butadiene, 1-chloro-1,3-butadiene, butadiene, isoprene, ethylene, styrene and acrylonitrile.

The monomer copolymerized with chloroprene is not limited to one type, and for example, one obtained by copolymerizing three or more types of monomers containing chloroprene can also be used. Further, the polymer structure of the chloroprene polymer is not particularly limited.

On the other hand, chloroprene rubber is roughly classified into sulfur-modified chloroprene rubber and non-sulfur-modified chloroprene rubber, and non-sulfur-modified chloroprene rubber is further classified into mercaptan-modified chloroprene rubber and xanthate-modified chloroprene rubber according to the type of molecular weight modifier. Sulfur. The sulfur-modified chloroprene rubber is obtained by copolymerizing sulfur with a raw material monomer containing chloroprene as a main component, and plasticizing the obtained copolymer with thiuram disulfide to adjust the viscosity to a predetermined Mooney viscosity.

On the other hand, the mercaptan-modified chloroprene rubber can be obtained by using alkyl mercaptans such as n-dodecyl mercaptan, tert-dodecyl mercaptan and octyl mercaptan as the molecular weight modifier. Further, the xanthate-modified chloroprene rubber can be obtained by using an alkylxanthogen compound as a molecular weight modifier. The chloroprene rubber blended in the rubber composition of the present embodiment may be any of the various chloroprene rubbers described above.

Further, the chloroprene rubber can be classified into, for example, a type having a slow crystallization rate, a type having a moderate crystallization rate, a type having a high crystallization rate, and the like based on the crystallization rate. Then, as the rubber composition of the present embodiment, any of the above-mentioned types of chloroprene rubber may be used, and can be appropriately selected depending on the intended use and the like.

The method for producing the chloroprene rubber is not particularly limited, but the raw material monomer may be polymerized by a commonly used emulsion polymerization method in the presence of an emulsifier, a polymerization initiator, a molecular weight modifier and the like. At that time, the emulsifier includes, for example, a saturated or unsaturated aliphatic alkali metal salt having 6 to 22 carbon atoms, an alkali metal salt of logonic acid or disproportionate logonic acid, and a formalin condensate of β-naphthalene sulfonic acid. An emulsifier generally used for emulsion polymerization of chloroprene, such as an alkali metal salt, can be used.

In addition, the polymerization initiator is generally used for emulsion polymerization of chloroprene, such as organic peroxides such as potassium persulfate, ammonium persulfate, sodium persulfate, hydrogen peroxide and tert-butyl hydroperoxide. A known polymerization initiator can be used.

The polymerization temperature at the time of emulsion polymerization is not particularly limited, but is preferably 0 to 50 ° C., more preferably 20 to 50 ° C. from the viewpoint of productivity and polymerization stability. .. The final conversion rate of the monomer is also not particularly limited, but is preferably in the range of 60 to 90% from the viewpoint of productivity.

Then, when the final conversion rate reaches a predetermined range, a small amount of a polymerization inhibitor is added to the polymerization solution to stop the polymerization reaction. At that time, examples of the polymerization inhibitor include thiodiphenylamine and 4-tert. Commonly used ones such as −butylcatechol and 2,2-methylenebis-4-methyl-6-tert-butylphenol can be used. After the polymerization reaction, for example, after removing the unreacted monomer by a steam stripping method or the like, the pH of the latex is adjusted, and the polymer is subjected to a conventional method such as freeze-coagulation, washing with water and hot air drying. Can be isolated.

[[ETA extraction amount]]
In the rubber composition of the present embodiment, if necessary, the extraction amount (ETA extraction amount) of the ethanol / toluene azeotropic mixture specified in JIS K 6229 of chloroprene rubber is 3.0 to 9.0% by mass. Can be a range. This makes it possible to further enhance the flame-retardant effect. By setting the ETA extraction amount of the chloroprene rubber to 3.0% by mass or more, the mechanical strength of the vulcanized product of the obtained chloroprene rubber composition can be further improved. Further, by setting the ETA extraction amount to 9.0% by mass or less, the effect of improving the flame retardancy of the obtained chloroprene rubber composition is further improved, and it is difficult to make the composition into a vulcanized product or a molded product. The effect of improving flammability can be further improved.

For the ETA extraction amount (mass%), the cut chloroprene rubber is placed in a eggplant-shaped flask attached to a condenser and extracted with ETA (a mixed solution of 70 volumes of ethanol and 30 volumes of toluene), and the ETA extract and chloroprene before extraction It can be calculated from the weight ratio of rubber. Examples of the components contained in the ETA extract include rosin acids and fatty acids, free sulfur and free plasticizers.

The ETA extraction amount is calculated by measuring the mass (A) of the chloroprene rubber before ETA extraction, measuring the mass (B) of the solid content obtained by drying the ETA extract, and calculating A / B × 100. The amount of ETA extracted can be appropriately adjusted by changing the amount of the compound added at the time of emulsion polymerization, the polymerization rate of the chloroprene rubber, and the like.

[Hydrotalcite compounds]
Hydrotalcite compounds exert a function of improving the flame retardancy of the rubber composition by a synergistic effect with specific aluminum hydroxide described later. However, if the BET specific surface area of the hydrotalcite compound is ^{less than 3 m 2} / g, the desired mechanical strength may not be obtained when it is made into a vulcanized product or a molded product. Further, when a hydrotalcite compound having a BET specific surface area ^{of more than 50 m 2} / g is used, the life of the unvulcanized compound is shortened, and the scorch may not be able to contribute to the vulcanized product. Therefore, in this embodiment, a hydrotalcite compound having a BET specific surface area of 3 to 50 m ^{2 / g is used.}

The above-mentioned BET specific surface area is a value measured by the one-point method defined in JIS Z8830. The BET method, the surface on the occupied area of known molecules (typically, N ₂ gas) of the powder particles to adsorb a method for determining the specific surface area of the sample powder from the adsorbed amount.

Further, as the hydrotalcite compounds, those represented by the chemical structural formula (1) can be used to further enhance the flame retardancy improving effect.
_{M x Al y (OH) z} CO 3 · mH 2 O (1)
Here, in the formula, M is a divalent metal ion consisting of at least one of Mg or Zn, x is 3 to 7, y is 1 to 3, z is 7 to 20, and m is 2 to 7. It is a numerical value.

Further, when the blending amount of the hydrotalcites compound is less than 4 parts by mass per 100 parts by mass of the chloroprene rubber, the flame retardancy of the rubber composition is not improved, or the unvulcanized compound is burnt and cannot be vulcanized. In addition, if it is blended in an amount exceeding 16 parts by mass, vulcanization inhibition or the like occurs and the mechanical strength of the vulcanized product tends to decrease. Therefore, in the rubber composition of the present embodiment, ^{4 to 16 parts by mass of a specific hydrotalcite compound having a BET specific surface area in the range of 3} to 50 m 2 / g is blended per 100 parts by mass of chloroprene rubber.

[Aluminum hydroxide]
Aluminum hydroxide has the effect of improving the flame retardancy of the rubber composition due to the synergistic effect with the above-mentioned hydrotalcite compounds. However, when the central particle size of aluminum hydroxide is less than 0.5 μm, the effect of improving flame retardancy may be reduced due to poor dispersion, or the processability of the compound may be deteriorated. Further, even when aluminum hydroxide having a central particle size of more than 5 μm is used, the effect of improving flame retardancy may be reduced due to poor dispersion, and the smoothness of the compound surface may be lost, resulting in molding failure.

The above-mentioned central particle size means the median diameter obtained by the laser diffraction method described in JIS Z 8825, that is, the particle size at which the integrated value in the measured particle size distribution is 50%.

Further, when the blending amount of aluminum hydroxide is less than 10 parts by mass per 100 parts by mass of chloroprene rubber, the effect of improving the flame retardancy of the rubber composition may be insufficient, and it exceeds 80 parts by mass. When blended, the mechanical strength of the vulcanized product may be significantly reduced. Therefore, in the rubber composition of the present embodiment, 10 to 80 parts by mass of aluminum hydroxide having a central particle size in the range of 0.5 to 5 μm is blended per 100 parts by mass of chloroprene rubber.

[Brominated organic compounds]
The rubber composition of the present embodiment can be blended with a bromine-containing organic compound, if necessary, whereby the flame retardancy of the chloroprene rubber can be further improved. The bromine-containing organic compound preferably has a bromine content of 60 to 85%. Flame retardancy can be further improved by using a bromine-containing organic compound having a bromine content of 60% or more, and mechanical strength can be further improved by using a bromine-containing organic compound having a bromine content of 85%. Can be made to.

Then, it is preferable to blend the bromine-containing organic compound in the range of 2 to 16 parts by mass per 100 parts by mass of the chloroprene rubber. By setting the blending amount of the bromine-containing organic compound to 2 parts by mass or more per 100 parts by mass of the chloroprene rubber, the flame retardancy of the chloroprene rubber can be further improved. Further, the mechanical strength can be further improved by setting the blending amount of the bromine-containing organic compound to 16 parts by mass or less per 100 parts by mass of the chloroprene rubber.

Here, as the bromine-containing organic compound, ethylenebis (pentabromophenyl), hexabromobenzene, tetrabromobisphenol S, tris (2,3-dibromopropyl) isocyanurate, tris (tribromoneopentyl) phosphate, bis ( 3,5-Dibromo-4-dibromopropyloxyphenyl) sulfone, tetrabromocyclooctane, tetrabromobisphenol anhydride, decabromodiphenyl ether, tetrabromobisphenol A, tetrabromobisphenol A bis (2-hydroxyethyl) ether, tetrabromobisphenol A epoxy oligomer, tetrabromobisphenol A carbonate oligomer, tetrabromobisphenol A bis (dibromopropyl ether), tetrabromobisphenol A bis (allyl ether), 1,2-bis (2,4,6-tribromophenoxy) ethane, 2,4,6-Tris (2,4,6-tribromophenoxy) 1,3,5-triazine, ethylenebistetrabromophthalimide, brominated polystyrene, polybrominated styrene, pentabromotoluene, hexabromocyclododecane, Brobrominated cycloalkane, etc. may be mentioned. It should be noted that these may be used in combination of two or more.

[Other ingredients]
Further, the rubber composition of the present embodiment contains various polymers and compounding chemicals usually used in the rubber industry, such as elastomer components and fillers other than chloroprene rubber, as long as flame retardancy and mechanical strength are not impaired. , Vulcanization agent, vulcanization accelerator, scorch inhibitor, processing aid and the like can be blended.

The rubber composition of the present embodiment can be produced in the same manner as a normal rubber composition. Specifically, it is obtained by kneading chloroprene rubber, hydrotalcite, aluminum hydroxide and other components at a temperature equal to or lower than the vulcanization temperature with a kneader such as a kneader, banbury or roll.

As described in detail above, since the rubber composition of the present embodiment contains a specific amount of a specific aluminum hydroxide together with a specific hydrotalcite compound with the chloroprene rubber, the mechanical strength is lowered. The flame retardancy of the vulcanized product can be dramatically improved without the need for it.

<Vulcanized product>
The vulcanized product of the present embodiment is obtained by molding and vulcanizing the above-mentioned rubber composition into a shape according to a purpose. At that time, the vulcanization method of the rubber composition is not particularly limited, and for example, press vulcanization, injection vulcanization, direct kettle vulcanization, indirect kettle vulcanization, and direct steam continuous vulcanization during or after molding. , Normal pressure continuous vulcanization or a vulcanization method such as a continuous vulcanization press may be used for vulcanization.

Further, the vulcanization conditions such as the vulcanization temperature and the vulcanization time are not particularly limited and can be set as appropriate, but the vulcanization temperature is 130 to 200 ° C. from the viewpoint of productivity and processing safety. The temperature is preferably 140 to 190 ° C., and more preferably 140 to 190 ° C.
Here, "machining safety" is a machining characteristic evaluated by the scorch time, and has a great influence on the defect occurrence rate. Specifically, when the scorch time is short, the unvulcanized rubber component is vulcanized during molding at a high temperature, and the frequency of molding defects increases.

Since the vulcanized product of the present embodiment uses the above-mentioned rubber composition, the flame retardancy is significantly improved as compared with the conventional vulcanized product using chloroprene rubber while maintaining good mechanical strength. Can be improved. Therefore, the vulcanized product of the present embodiment is used for molded products that require high flame retardancy, such as buildings and structures that require flame retardancy, and rubber parts for ships, railways, coal mines, automobile fields, and the like. Can also be preferably used.

Hereinafter, the present invention will be described in more detail based on Examples. It should be noted that the examples described below show an example of a typical example of the present invention, and the scope of the present invention is not narrowly interpreted by this.

In this example, chloroprene rubber is produced by a predetermined method, various components including the rubber component are blended in the compositions shown in Tables 1 and 2, and then kneaded using an 8-inch roll to form the example and the example. A rubber composition of a comparative example was prepared. Then, each rubber composition of Examples and Comparative Examples was vulcanized and its performance was evaluated. Details will be shown below.

<Manufacturing of chloroprene rubber (A)>
Using a reactor with an internal volume of 30 liters, 120 parts by mass of water, 3.8 parts by mass of disproportionated potassium torrodinate (manufactured by Harima Kasei Group Co., Ltd., the same applies hereinafter), β-naphthalene sulfonate sodium salt under a nitrogen stream. (Demol NL: manufactured by Kao Co., Ltd., the same applies hereinafter) Add 0.5 parts by mass, 0.8 parts by mass of sodium hydroxide and 0.3 parts by mass of sodium sulfite as other additives, dissolve, and stir to make a single amount of chloroprene. 100 parts by mass of body and 0.10 parts by mass of n-dodecyl mercaptan were added. Then, using 0.1 part by mass of potassium persulfate as a catalyst, polymerization was carried out at 40 ° C. under a nitrogen atmosphere, and when the final polymerization rate reached 70%, an emulsion of phenothiazine was added to stop the polymerization, and the polymerization was stopped under reduced pressure. The unreacted monomer was removed. Subsequently, the pH of the chloroprene latex was adjusted to 7.0 with dilute acetic acid, and then the chloroprene polymer was obtained by freeze-coagulation and drying in a conventional manner. The obtained chloroprene polymer was molded into a rubber sheet to produce chloroprene rubber (A).

<Manufacturing of chloroprene rubber (B)>
Using a reactor with an internal volume of 30 liters, 120 parts by mass of water, 9.5 parts by mass of disproportionated potassium torrodinate, 1.0 part by mass of β-naphthalene sulfonic acid sodium salt (Demor NL), etc. 1.0 part by mass of sodium hydroxide and 0.3 part by mass of sodium sulfite were charged as additives, and after dissolution, 100 part by mass of chloroprene monomer and 0.10 part by mass of n-dodecyl mercaptan were added with stirring. Then, using 0.05 parts by mass of potassium persulfate as a catalyst, polymerization was carried out at 40 ° C. under a nitrogen atmosphere, and when the final polymerization rate reached 85%, an emulsion of phenothiazine was added to stop the polymerization, and the polymerization was stopped under reduced pressure. The unreacted monomer was removed. Subsequently, the pH of the chloroprene latex was adjusted to 7.0 with dilute acetic acid, and then the chloroprene polymer was obtained by freeze-coagulation and drying in a conventional manner. The obtained chloroprene polymer was molded into a rubber sheet to produce chloroprene rubber (B).

<Manufacturing of chloroprene rubber (C)>
Using a reactor with an internal volume of 30 liters, 120 parts by mass of water, 1.2 parts by mass of potassium disproportionate torrodinate, 0.2 parts by mass of β-naphthalene sulfonate sodium salt (Demol NL), etc. 0.3 parts by mass of sodium hydroxide and 0.3 parts by mass of sodium sulfite were charged as additives, and after dissolution, 100 parts by mass of chloroprene monomer and 0.10 parts by mass of n-dodecyl mercaptan were added with stirring. Then, using 0.3 parts by mass of potassium persulfate as a catalyst, polymerization was carried out at 40 ° C. under a nitrogen atmosphere, and when the final polymerization rate reached 63%, an emulsion of phenothiazine was added to stop the polymerization, and the polymerization was stopped under reduced pressure. The unreacted monomer was removed. Subsequently, the pH of the chloroprene latex was adjusted to 7.0 with dilute acetic acid, and then the chloroprene polymer was obtained by freeze-coagulation and drying in a conventional manner. The obtained chloroprene polymer was molded into a rubber sheet to produce chloroprene rubber (C).

<Measurement of ETA extraction amount>
Each 6 g of each obtained chloroprene rubber was cut into 2 mm squares, placed in an eggplant-shaped flask equipped with a condenser, and the non-rubber component was extracted by ETA. The ETA extraction amount (mass%) is calculated from the weight ratio of the ETA extract and the chloroprene rubber. The chloroprene rubber (A) is 5.1% by mass, the chloroprene rubber (B) is 9.3% by mass, and the chloroprene rubber (C). Was 2.8% by mass.

The compounding components shown in Tables 1 and 2 are as follows.
-Chloroprene rubber (A) (ETA extraction rate: 5.1% by mass)
-Chloroprene rubber (B) (ETA extraction rate: 9.3% by mass)
-Chloroprene rubber (C) (ETA extraction rate: 2.8% by mass)
・ Carbon Black SRF (Asahi # 50 manufactured by Asahi Carbon Co., Ltd.)
・ Stearic acid (Stearic acid 50S manufactured by New Japan Chemical Co., Ltd.)
・ Amine-based anti-aging agent (N-Phenyl-1-naphthylamine manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.)
・ Magnesium oxide # 150 (Kyowa Mag 150 manufactured by Kyowa Chemical Industry Co., Ltd.)
· Hydrotalcite (A) (Kyowa Chemical Industry Co., Ltd. _{DHT-4A Mg 4.5 Al 2 (} OH) 13 CO 3 · 3.5H 2 O (BET specific surface area: ^10m 2 / g))
· Hydrotalcite (B) (Kyowa Chemical Industry Co., Ltd. alk Mac _{SH Mg 6 Al 2 (OH)} 16 CO 3 · 4H 2 O (BET specific surface area: 102m ² / g))
-Aluminum hydroxide (A) (Heidilite H-42M manufactured by Showa Denko KK (center particle size: 1.0 μm))
-Aluminum hydroxide (B) (Heidilite H-21 manufactured by Showa Denko KK (center particle size: 27 μm))
-Brominated organic compound (A) (ethylenebis (pentabromophenyl), bromine content: 82%)
-Brominated organic compound (B) (hexabromobenzene, bromine content: 87%)
-Brominated organic compound (C) (tetrabromobisphenol S, bromine content: 56%)
・ Thiourea vulcanization accelerator (Axel 22S manufactured by Kawaguchi Chemical Industry Co., Ltd .: ethylene thiourea)
・ Zinc oxide (2 types of zinc oxide manufactured by Sakai Chemical Industry Co., Ltd.)

<Preparation of evaluation sample>
Using the chloroprene rubber prepared by the above method, the mixture of Examples 1 to 12 and Comparative Examples 1 to 7 shown in Tables 1 and 2 was mixed using an 8-inch roll, and press-crosslinked at 160 ° C. for 20 minutes. Then, a test piece for evaluation was prepared.

<Evaluation>
Using the test piece prepared above, "tensile strength (TB), elongation at break (EB)", "hardness (HS)", "workability" and "oxygen index" were evaluated.

"Tensile strength (TB) and elongation at break (EB)" were measured in accordance with JIS K6251. The "hardness (HS)" was measured using a durometer hardness meter in accordance with JIS K6253. Furthermore, the "oxygen index" was measured according to JIS K6269. Here, the higher the value of the oxygen index, the higher the flame retardancy.

On the other hand, in the evaluation of "processability", the produced chloroprene rubber composition was evaluated in a complex manner from the viewpoint of roll processability and dispersibility of additives. The roll processability was rated as ◯ when there was no problem with roll workability, and as x when the work was hindered due to shrinkage of the compound or the like. Regarding the dispersibility of the additive, the compound diluted to 1 mm was visually confirmed, and was rated as ◯ when no undissolved component, foreign matter, or agglutinate was observed, and as x when it was observed.

<Result>
The results are shown in Tables 1 and 2 below.

<Discussion>
The test pieces obtained by vulcanizing the chloroprene rubber compositions of Examples 1 to 12 shown in Table 1 have tensile properties (compared to the test pieces obtained by vulcanizing the chloroprene rubber compositions of Comparative Examples 1 to 7 shown in Table 2). While maintaining good mechanical strength such as tensile strength (TB) and elongation at break (EB)), the flame retardancy was also excellent.

Considering the comparative example in detail, Comparative Example 1 containing no hydrotalcite compound or a flame retardant such as aluminum hydroxide had good mechanical strength but very low flame retardancy. In Comparative Example 2 in which the amount of the hydrotalcite compound compounded with respect to 100 parts by mass of chloroprene rubber was less than 4 parts by mass, the unvulcanized compound was burnt and could not be vulcanized, and flame retardancy could not be evaluated. .. In Comparative Example 3 in which the amount of the hydrotalcite compound compounded with respect to 100 parts by mass of the chloroprene rubber exceeded 16 parts by mass, the flame retardancy was good, but the mechanical strength was very low.

In Comparative Example 4 in which the blending amount of aluminum hydroxide was less than 10 parts by mass with respect to 100 parts by mass of the chloroprene rubber, the mechanical strength was good, but the flame retardancy was very low. In Comparative Example 5 in which the amount of aluminum hydroxide compounded with respect to 100 parts by mass of chloroprene rubber exceeded 80 parts by mass, the flame retardancy was good, but the mechanical strength was very low.

Comparative Example 6 using hydrotalcite compounds having a BET specific surface area ^{outside the range of 3} to 50 m 2 / g had a short life of the unvulcanized compound and could not contribute to the vulcanized product by the scorch.

In Comparative Example 7 using aluminum hydroxide outside the range of the central particle size of 0.5 to 5 μm, the flame retardancy was very low due to poor dispersion.

Considering the examples in detail, Example 7 in which the bromine-containing organic compound having a bromine content of 60 to 85% was blended in the range of 2 to 16 parts by mass per 100 parts by mass of the chloroprene rubber did not contain the bromine-containing organic compound. The flame retardancy was improved as compared with Example 6. Even if a bromine-containing organic compound having a bromine content of 60 to 85% was blended, Example 8 blended in excess of 16 parts by mass per 100 parts by mass of chloroprene rubber was blended in the range of 2 to 16 parts by mass. Compared with No. 7, the flame retardancy was high, but the mechanical strength was slightly lower.

Example 9 containing a bromine-containing organic compound having a bromine content of more than 85% had the same flame retardancy as Example 7 containing a bromine-containing organic compound having a bromine content of 60 to 85%. However, the result was that the mechanical strength was slightly low. Example 10 containing a bromine-containing organic compound having a bromine content of less than 60% had the same mechanical strength as Example 7 containing a bromine-containing organic compound having a bromine content of 60 to 85%. However, the result was that the flame retardancy was slightly low.

Example 11 using the chloroprene rubber (B) having an ETA extraction amount of more than 9.0% by mass is an example using the chloroprene rubber (A) having an ETA extraction amount in the range of 3.0 to 9.0% by mass. Compared with No. 7, the mechanical strength was the same, but the flame retardancy was slightly lower. Example 11 using the chloroprene rubber (C) having an ETA extraction amount of less than 3.0% by mass is an example using the chloroprene rubber (A) having an ETA extraction amount in the range of 3.0 to 9.0% by mass. Compared with No. 7, the flame retardancy was the same, but the mechanical strength was slightly lower.

<Application study>
When rubber parts that can be used in the fields of buildings, structures, ships, railways, coal mines, automobiles, etc. were manufactured using the rubber compositions of Examples 1 to 12, flame retardancy without deterioration of mechanical strength was produced. Was excellent.

Claims (4)

For 100 parts by mass of chloroprene rubber
(A) represented by the following chemical formula (1), hydrotalcite compound BET specific surface area measured by a one-point method specified in JIS Z8830 is ^{_{3~50m 2 / g M x Al y}} (OH) z CO ₃ · _mH 2 O (1)
(In the formula, M is a divalent metal ion consisting of at least one of Mg or Zn, x is 3 to 7, y is 1 to 3, z is 7 to 20, and m is a coefficient value in the range of 2 to 7. Shown) with 4 to 16 parts by mass,
(B) 10 to 80 parts by mass of aluminum hydroxide having a central particle size of 0.5 to 5.0 μm obtained by the laser diffraction method described in JIS Z 8825.
Contains ,
The chloroprene rubber is a flame-retardant rubber composition , wherein the extraction amount of the ethanol / toluene azeotropic mixture defined by JIS K 6229 is 3.0 to 9.0% by mass. Bromine content from 60 to 85% of bromine-containing organic compound, the flame retardant rubber composition according to claim 1, characterized in that it contains 2 to 16 parts by weight per the chloroprene rubber 100 parts by weight. The vulcanized product of the rubber composition according to claim 1 or 2. A molded product made of the vulcanized product according to claim 3.