JPH06172548A - Production of rubber molding and rubber composition - Google Patents

Abstract

PURPOSE:To provide a rubber compsn. which is excellent in extrudability, can be vulcanized continuously, and gives a rubber including exhibiting a high heat resistance and a low compression set. CONSTITUTION:A rubber component comprising 10-90wt.% DCP-base EPDM and 90-10wt.% chlorinated polyethylene is mixed with an org. peroxide crosslinker, a filler, etc., to give an unvulcanized mixture 2, which is extruded with an extruder 1 and thermally vulcanized with a thermal vulcanizer 3. The mixture is excellent in extrudability, can be vulcanized continuously, and gives a rubber molding exhibiting a high heat resistance and a low compression set.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rubber molded article which is capable of continuous vulcanization, is excellent in extrusion moldability and heat resistance, and has a small compression set, and a rubber composition.

[0002]

2. Description of the Related Art A rubber molded article is generally excellent in elasticity and has a property of being less likely to be damaged even when deformed or bent. Therefore, it is widely used for automobile parts and daily necessities. By the way, in producing the above-mentioned rubber molded article, first, a vulcanization accelerator such as sulfur or organic peroxide is added to a natural or synthetic rubber raw material. Next, these are mixed and extrusion-molded.

Then, the rubber molecules are vulcanized under a relatively high temperature of 180 to 220 ° C. to vulcanize (crosslink) between the rubber molecules. As a result, a rubber molded product having elasticity can be obtained. There are various synthetic rubber raw materials, and for example, ethylene-propylene copolymer (EPDM) is used.

The EPDM is a copolymer of monomers of ethylene, propylene and a third component. An organic compound having an unsaturated bond in the side chain is used as the third component. Examples of the organic compound include dicyclopentadiene (DCP), ethylidene norbornene (E
NB), 1,4-hexadiene (1,4-HD) and the like.

The EPDM having the above DCP as the third component is D
It is called CP EPDM, and the one using ENB as the third component is called ENB EPDM. EPDM above
Generally, sulfur (S) or peroxide (organic peroxide) is used as a vulcanization accelerator (crosslinking agent).

Therefore, thermal vulcanization using sulfur as a crosslinking agent is called sulfur vulcanization, and vulcanization using a peroxide crosslinking agent is called thermal vulcanization. The rubber molded product obtained by the former is
Generally, it has a large compression set and is easily deformed.
On the other hand, the rubber molded product obtained by the latter has a small compression set. Therefore, when a rubber molded product having a small compression set is desired, it is manufactured by the latter thermal vulcanization method.

[0007]

However, the above-mentioned conventional technique has the following problems. That is, in the above thermal vulcanization, the rubber molecules on the surface portion of the EPDM are cut and decomposed by the organic peroxide and oxygen in the air. for that reason,
The surface of the EPDM rubber molded product becomes sticky.

As a result, continuous vulcanization cannot be performed by continuously performing work from extrusion molding to the end of thermal vulcanization, and a rubber molded product having a desired shape cannot be continuously manufactured. Further, the DCP-based EPDM is unlikely to be decomposed by the organic peroxide and oxygen in the air. However, grades with excellent workability during extrusion molding (hereinafter referred to as extrusion moldability) have not been marketed and are not suitable for extrusion molding with irregular cross-sections.

As described above, the present invention uses a DCP EPDM having a small compression set and excellent heat resistance,
The focus is on continuously producing rubber molded products. The present invention has been made in view of such conventional problems, and provides a method for producing a rubber molded article and a rubber composition, which are capable of continuous vulcanization, are excellent in extrusion moldability and heat resistance, and have a small compression set. It is the one we are trying to provide.

[0010]

DISCLOSURE OF THE INVENTION The present invention relates to DCP EPDM10s.
90% (wt%) and chlorinated polyethylene 90-10
% Of the rubber component, the crosslinking agent of the organic peroxide, and the additive component such as a filler are mixed to form an unvulcanized mixture, and the unvulcanized mixture is extruded, and then hot air is added. The method for producing a rubber molded article is characterized in that it is thermally vulcanized below.

What is most noticeable in the present invention is that a rubber component obtained by mixing the above DCP EPDM and chlorinated polyethylene in a specific ratio is added in the presence of an organic peroxide.
That is, a rubber molded product is obtained by continuous vulcanization under hot air.
The DCP-based EPDM is a dicyclopentadiene (DC
It is an ethylene-propylene copolymer containing P) as the third component.

The above DCP EPDM has excellent ozone resistance and weather resistance because it has no unsaturated bond in the main chain.
Moreover, since sulfur is not used as a cross-linking agent, it has excellent stain resistance and scorch stability. This is because the migration of sulfur does not occur in the adjacent members.

The above chlorinated polyethylene is a random chlorinated product produced by a chlorine substitution reaction of polyethylene, and its structure is considered to be a three-component copolymer of ethylene, vinyl chloride and 1,2-dichloroethylene. The above-mentioned chlorinated polyethylene is a non-crystalline elastomer having a chlorine content of 25 to 45%. Those with a relatively low chlorine content are similar to those of polyethylene, and those with a relatively high chlorine content are similar to those of polyvinyl chloride.

Here, the rubber component is the DCP type E.
The PDM is 10 to 90% by weight (hereinafter,% by weight) and the chlorinated polyethylene is 90 to 10%. DCP EP
If the DM exceeds 90%, the compression set increases, while if the DCP EPDM is less than 10%, the extrusion moldability deteriorates.

Examples of the organic peroxide include 1,3
Bis (tertiary butylperoxyisopropyl) benzene,
2,5 Dimethyl 2,5 (tertiary butylperoxy) hexyne-3, dicumyl peroxide is used. The organic peroxide is added so that the amount of active oxygen is 0.005 to 0.02 mol with respect to 100% of the rubber component. As the above-mentioned additional component, in addition to the filler, for example, a crosslinking accelerator,
Acid acceptors, softeners, antioxidants, processing aids, defoamers, etc. The above-mentioned filler improves physical properties such as strength and serves as an extender. For example, kaolin clay, talc, mica, calcium carbonate and silica are used.

The cross-linking accelerator acts together with the organic peroxide cross-linking agent (vulcanizing agent) to enhance the vulcanization rate in a small amount. For example, triallyl isocyanurate and stearic acid are used. The acid acceptor is for catching chlorine gas (Cl ₂ ) dissociated from the chlorinated polyethylene so as not to evaporate. For example, magnesium oxide (Mg
O) is used.

The softening agent is for facilitating the kneading when mixing the rubber component and the additive component, and for example, paraffin oil is used. The processing aid improves the extrudability of the unvulcanized mixture, and is, for example, a polymeric fatty acid ester. Here, the extrusion moldability means the quality of workability during extrusion molding and thermal vulcanization of the unvulcanized mixture.

The defoaming agent removes bubbles generated in the unvulcanized mixture, and for example, calcium oxide (CaO) is used. The unvulcanized mixture is a compound that has not been subjected to extrusion molding and thermal vulcanization.

The extrusion molding is carried out by using a machine for continuously extruding the unvulcanized mixture from a die with, for example, a screw. The thermal vulcanization is carried out, for example, under hot air at 180 to 240 ° C. using a high frequency (microwave) heating device or a hot air heating device. Then, the extrusion molding and the thermal vulcanization are performed by a continuous continuous operation. This is referred to as continuous vulcanization in the present invention.

The rubber composition of the present invention is DC
P-based EPDM 10 to 90% and chlorinated polyethylene 90
It is obtained by thermally vulcanizing an unvulcanized mixture containing a rubber component composed of 10% by weight, an organic peroxide crosslinking agent, and an additive component such as a filler.

This rubber composition can be obtained, for example, by the above-mentioned production method or without extrusion molding in the above-mentioned production method. This rubber composition can be processed into a desired shape by slicing, punching or the like. The rubber molded product is widely used for automobile parts of various shapes and daily necessities.

[0022]

In the method for producing a rubber molded article of the present invention, a rubber component obtained by mixing 10 to 90% of DCP EPDM and 90 to 10% of chlorinated polyethylene is used. Therefore, it has excellent extrusion moldability during mixing and extrusion of rubber components.

As described above, the reason why the extrudability is excellent is that the unvulcanized mixture is increased in thermal softening property by mixing the chlorinated polyethylene, and the whole unvulcanized mixture is increased in tackiness and fluidity. It is considered that this is because workability during extrusion molding when compounding the sulfur mixture is improved. Further, since the above-mentioned organic peroxide is used as the cross-linking agent, the compression set of the rubber molding is significantly smaller than that of sulfur vulcanization using sulfur.

Further, since the above-mentioned unvulcanized mixture is used, the DCP EPDM does not undergo decomposition or heat aging due to the organic peroxide and oxygen in the air during thermal vulcanization. Therefore, continuous vulcanization is possible and heat resistance is improved. Therefore, according to the present invention, it is possible to provide a method for producing a rubber molded article and a rubber composition which are capable of continuous vulcanization, are excellent in extrusion moldability and heat resistance, and have a small compression set.

[0025]

【Example】

Example 1 A method for producing a rubber molded article and a rubber composition according to an example of the present invention will be described with reference to FIGS. 1 and 2 and Tables 1 and 2. In the method for manufacturing a rubber molded article of this example, as shown in FIG. 1, an unvulcanized mixture 2 is extruded by an extruder 1 and then thermally vulcanized by a thermal vulcanizer 3 under hot air. , Then cool.

The unvulcanized mixture 2 is a DCP type EPDM.
10 to 90% (hereinafter, referred to as weight%) and 90 to 10% of chlorinated polyethylene are mixed in a rubber component, a crosslinking agent of an organic peroxide, and an additive component such as a filler. Become.

Further, as shown in FIG. 1, the unvulcanized mixture 2 is supplied to a hopper 11 provided above the extruder 1.
Throw more. Then, through an extrusion molding port 12 arranged in front of the extrusion molding machine 1, an extrusion molded product 13 having a predetermined shape is continuously molded. The extruded product 13 is heated under hot air in a first vulcanizing step A in which a microwave heating device 31 is used for heat vulcanization and a second vulcanizing step B in which a hot air heating device 32 is used for heat vulcanization. Heat vulcanized.

A heated atmosphere of 200 to 220 ° C. is used as the hot air. After that, the heat-vulcanized product 33 is cooled by using the water cooling device 4 as shown in FIG. As a result, a rubber molded product having a predetermined shape is obtained.

Next, samples 1 to 5 according to this example and comparative examples C1 to C4 were evaluated for continuous vulcanizability and the like. That is,
First, DCP EPDM and chlorinated polyethylene are mixed in a specific ratio to adjust a rubber component, and then an organic peroxide or the like is mixed with the rubber component to form an unvulcanized mixture.

Thereafter, as shown in FIG. 2, a rubber molded product 6 having a predetermined shape is obtained by using the Garvey die 5. And
For this rubber molded product 6, as shown in Tables 1 and 2, the continuous vulcanizability (surface condition after thermal vulcanization), extrusion moldability, heat aging (heat resistance), and compression set were measured. Sample 1
5, each condition of Comparative Examples C1 to C4 and the measurement results thereof are shown in Tables 1 and 2.

[0031]

[Table 1]

[0032]

[Table 2]

The above physical properties were measured by the following methods. The continuous vulcanizability is workability in which the unvulcanized mixture 2 can be continuously processed from the extrusion molding step to the end of thermal vulcanization.

The extrudability is measured according to ASTM D22.
According to No. 30, the Garvey die 5 is used as shown in FIG. That is, the state of the skin 63 on the surface of the extruded rubber molded product 6 is observed and evaluated by the four-step evaluation method of 4 to 1. Further, in order to check the fidelity with respect to a predetermined size and shape, as shown in FIG. 2, the presence or absence of the swell 61 of the rubber molded product 6, the molding accuracy of the edge 62, and the molding accuracy of the corner 64. Therefore, the evaluation is performed by the four-step evaluation method of 4 to 1.

The edge 62 is formed by the Garvey die 5
The shape of the X portion and the corner 64 are evaluated as 4, 3, 2, 1 in the order corresponding to the shape of the Y and Z portions. this house,
Some corners 64 have a poor extrusion moldability, and some corners are in a splayed state. Further, the swell 61 is evaluated by the shape and size of the bulging protrusion formed on a part of the rubber molded product 6.

Here, the case where no swell 61 is generated is set to 4, and the shape and size of the generated swell 61 are evaluated. In addition, other evaluations relating to extrusion moldability are also shown in the table in the order of excellent (4) to inferior (1).

The compression set is based on JIS K-6301.
Residual strain due to heat compression of a rubber molded product was measured in accordance with the procedure described above and used in the parts subjected to static compression and shear force. The heat aging is performed according to JIS K6301, and after the rubber molded product is heat aged for a specified time (100 ° C. × 72 hrs), it is taken out from the gear type aging test and left at room temperature, and the tensile strength is within 16 to 96 hours, Elongation, tensile stress and hardness were measured.

Next, samples 1 to 5 of the present invention and samples C1 to C4 of the comparative example will be described with reference to Tables 1 and 2. In the table, as the DCP EPDM, JSR EP75F manufactured by Japan Synthetic Rubber Co., Ltd. was used. Also, as the chlorinated polyethylene, Eraslen 401AE manufactured by Showa Denko KK was used. Also, as the organic peroxide,
Dicumyl peroxide was used. In addition, these compounding amounts are all shown by weight%.

As the crosslinking accelerator, triallyl isocyanurate or a sulfur compound (TMTD, MBTS, MB
T, CBS, etc.) was used. As auxiliary components, stearic acid, processing aids (polymer fatty acid esters), fillers (CaCO ₃ , talc, etc.), softeners (paraffinic oil), defoamers (CaO) were used.

As is known from both tables, Samples 1 to 5 of the examples are all A for continuous vulcanization. Further, Comparative Examples C1 to C4 are all A. Regarding the extrusion moldability, as shown in Table 1, all of Samples 2 to 5 of the examples showed the best extrusion moldability of 4. Further, in the sample 1, all were 4 except that the edge 62 and the corner 64 were 3 (somewhat good). On the other hand, Comparative Example C
As shown in Table 2, C2 and C4 were 3 to 4 (somewhat good), but C1 and C3 were not as good as 1 to 3.

Regarding heat aging (heat resistance), the residual tensile strength of Samples 1 to 5 of the examples was 95 to 106, while that of Comparative Examples C1 to C4 was 66 to 110. From this, it can be seen that the present invention has excellent heat resistance. On the other hand, regarding the residual elongation, the samples 1 to 5 of the examples are 96 to 102, while the comparative examples C1 to C
4 was 94-108. From this, it can be seen that the present invention has excellent heat resistance.

Regarding the compression set, the samples 1 to 5 of the examples are as small as 12 to 20, while the comparative examples C1 to C1 are small.
C4 had a large variation range of 12 to 84 and was relatively large. From the above results, as a comprehensive evaluation, the samples 1 to 5 of the example are almost good, while the comparative examples C1 to C4 are
It turns out that is bad or not very good.

[Brief description of drawings]

FIG. 1 is a process drawing of a method for manufacturing a rubber molded product according to an embodiment.

FIG. 2 is a perspective view showing a production state of a sample by extrusion molding in an example.

[Explanation of symbols]

 1. ． ． Extruder, 2. ． ． Unvulcanized mixture, 3. ． ． Thermal vulcanizer, 5. ． ． Garvey dye, 6. ． ． Rubber moldings,

Claims (2)

[Claims] 1. A DCP EPDM of 10 to 90% (hereinafter,
% Means) and chlorinated polyethylene 90-1
A rubber component obtained by mixing 0%, an organic peroxide crosslinking agent, and an additive component such as a filler are mixed to form an unvulcanized mixture, and the unvulcanized mixture is extruded and then heat-treated. A method for producing a rubber molded article, which comprises thermally vulcanizing under air. 2. An unvulcanized mixture containing a rubber component consisting of 10 to 90% of DCP EPDM and 90 to 10% of chlorinated polyethylene, a crosslinking agent of organic peroxide, and an additive component such as a filler, A rubber composition obtained by thermal vulcanization.