JP2921131B2 - Rubber molded products for automobiles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a nitrile rubber (NB)
R) and polyvinyl chloride (PVC) (hereinafter, abbreviated as “NBR / PVC”). A rubber molded article for automobiles (hereinafter, “NBR / PVC molded”) molded from a rubber compound using rubber as a raw material rubber. Product).) In particular, a molded product such as a weather strip (including a door mirror mounting body, a window frame rubber, a door glass run, a seal rear guide), a handle, a molding (a door lower molding, a bumper molding), etc., having a design surface D on all or a part of the molded product. It is a rubber molded product for automobiles that can be expected to be applied to the automobile (see Figs. 1 and 2).

[0002] The blending units used in the present invention are weight units unless otherwise specified.

[0003]

2. Description of the Related Art In recent years, there has been a stronger demand for improved appearance quality, that is, improved design, of such rubber molded articles for automobiles as described above.

[0004]

However, the above-mentioned NBR /
In the case of a PVC molded article, there has been a problem that the design surface becomes rainbow-like or reddish over time, and the appearance quality deteriorates.

[0005] In view of the above, the present invention provides a rubber molded product made of NBR / PVC whose design surface is not easily degraded in appearance over time, such as a rainbow-like or reddish appearance. The purpose is to provide.

[0006]

The present invention solves the above-mentioned problems,
The problem is solved by the following configuration.

Using NBR / PVC as raw rubber , plasticizer
In a rubber molded article for automobiles, which is molded with a rubber compound which is essential, the extraction amount of a low molecular compound (methanol extraction) of the polyblend is less than 3% by weight, and the rubber compound is a stearic acid-free type. And
The amount of the plasticizer in the rubber compound is 20 phr.
Less than.

[0008]

[Detailed Description of Means] (1) The rubber molded article for automobiles of the present invention uses NBR / PVC as a raw rubber and requires a plasticizer as an essential component.
It is a prerequisite that it be molded with a rubber compound.

Here, rubber molded articles for automobiles include sealing parts such as mirror brackets (FIG. 1), window frame rubbers (FIG. 2), door glass runs, and exterior articles for automobiles such as side moldings. Etc. can be exemplified.

(2) In the present invention, the rubber compound is
The following requirements must be satisfied.

[0011] The polyblend has a low molecular weight compound extraction (methanol extraction) of less than 3%. When the extraction amount of the low-molecular compound exceeds 3%, the above-mentioned poor appearance over time tends to occur in the molded article.

Here, the extraction amount of the low molecular compound is based on the amount obtained by the following measuring method. "Polyblend sample (Thin between 0.2 mm gap rolls, shredded) 5
To 120 g of methanol, add 120 ml of methanol and boil under reflux. The extract is transferred to another container, heated to remove methanol, dried under reduced pressure, and the obtained compound is weighed. "The rubber compound is a stearic acid-free type. When stearic acid is contained, the above-mentioned poor appearance is likely to occur over time in a molded product.

The amount of the plasticizer in the rubber compound is
Less than 20 phr. If it exceeds 20 phr, the above-mentioned poor appearance is likely to occur over time, as described above. Here, as the plasticizer, dioctyl phthalate (DO) is usually used.
P) is used.

(3) The configuration other than the above essential requirements is not particularly limited, but is usually as follows.

The blend ratio of NBR / PVC is PVC
A general purpose material having a content of 10 to 60% can be used.
When the rubber molded product is a seal part, the PVC content is 20 to
40% is desirable. If it is less than 20%, problems are likely to occur in ozone resistance, abrasion resistance and the like, and the sliding resistance increases, which is not desirable. On the other hand, if it exceeds 40%, improvement in rebound resilience and compression set resistance cannot be expected.

Although the NBR is not particularly limited, the amount of bound acrylonitrile (AN amount) in the nitrile rubber is determined by considering the balance between the above-mentioned required physical properties such as polyblendability, cold resistance and compression set resistance. AN amount: 2
5-30%), middle and high nitrile (AN content: 31-35%)
Is desirable. If the AN amount is too low, the blendability with PVC is poor, and the strength tends to cause a problem. On the other hand, if the AN amount is too high, the rebound resilience and the compression set resistance required for the seal component are reduced.

From the viewpoint of resistance to compression set, PVC is
Those having a number average degree of polymerization of 1,000 to 1500 are used. The higher the degree of polymerization, the better. However, if the degree of polymerization is too high, the viscosity of the polymer increases, which tends to cause problems in moldability. PVC may be a homopolymer or a copolymer copolymerized with vinyl acetate or the like. In addition to the above auxiliary materials, NBR / PVC usually has NBR
And carbon black, zinc white, a vulcanizing agent, a vulcanization accelerator, an antioxidant and the like.

In the above, the amount of the carbon black is usually 30 to 80 phr. Below 30 phr,
It is difficult to obtain a predetermined strength for the vulcanized product, and if it exceeds 80 phr, problems tend to occur in compression set and rebound resilience.

(4) The above-mentioned NBR / PVC rubber composition is usually kneaded, then taken out into a sheet and cut into an appropriate length to obtain each molding material. Then, using the molding material, vulcanization molding is performed by a molding method such as extrusion, transfer, injection, or compression to form a rubber molded product such as a glass run.

[0020]

According to the NBR / PVC molded product of the present invention, the design surface becomes rainbow-like or reddish with time, as shown in the examples described below, due to the above-mentioned structure. It is unlikely that the appearance quality of such products deteriorates. Also, during molding, the mold is hardly stained, and the appearance quality is not easily degraded due to the mold stain.

The reason is presumed to be as follows. When the plasticizer is added in an amount of 20 phr or more, the plasticizer becomes a fluid medium for the vulcanization accelerator and the low-molecular compound in the additive polymer, and is easily deposited on the surface.

Generally, stearic acid used in a vulcanizing system and low molecular weight compounds in a polymer have poor compatibility with the polymer, and when the content is large, it is easy to precipitate on the surface.

What has eliminated the above-mentioned phenomena is the NBR / PVC molded product of the present invention.

[0024]

[Test Example] Each of the test pieces of Examples and Comparative Examples was prepared by using a rubber compound of each compounding formula shown in Table 1 and 100 kgf / cm ^2.
It was vulcanized under the conditions of × 160 ° C. × 15 min. To obtain a 2 mmt rubber sheet.

Each of the test pieces was subjected to an appearance evaluation test under the conditions shown in the display. As shown in Table 1,
In the examples satisfying the constitutional requirements of the present invention, appearance defects caused by rainbow / red spots did not occur.

Comparative Example 1 is an example in which the extraction amount of the low molecular weight compound of NBR / PVC exceeds 3%, Comparative Example 2 is an example in which the amount of the plasticizer exceeds 20%, and Comparative Example 3 is a compound containing stearic acid. This is an example.

[0027]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a partial perspective view of a mirror bracket which is an example of a molded article for an automobile to which the present invention can be applied.

FIG. 2 is a partial perspective view of the window frame rubber.

[Explanation of symbols]

 1 Mirror mounting part 3 Mounting leg part D Design surface

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C08L 9/02 C08K 5/12 C08L 27/06

Claims (1)

(57) [Claims] 1. A rubber molded article for automobiles formed by using a blend polymer of nitrile rubber and polyvinyl chloride as a raw rubber and a rubber compound containing a plasticizer as an essential component, comprising extracting a low molecular compound from the polyblend. The rubber compound is a stearic acid-free type, and the amount of the plasticizer in the rubber compound is 20 phr.
Less than, a rubber molded product.