JP2002012721A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve on various characteristics such as sealing capability, slidability and fatigue resistance of rubber composition products such as a sealing member like glass runners. SOLUTION: The 1st EPDM prepared by the ordinary polymerization method has an ethylene/propylene weight ratio of 70/30-90/10 with ethylene occupying a high percentage and is crystalline, then the 2nd EPDM is prepared having an ethylene/propylene weight ratio of 40/60-70/30. In the ordinary method to follow, the 1st EPDM, the 2nd EPDMs, and additives are brought into reaction for manufacturing a rubber preparation wherein the 1st EPDM/2nd EPDM weight ratio is 5/95-30/70. The rubber preparation is subjected to crosslinking for the completion of the rubber composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition mainly used for solid rubber such as glass run in automobiles.

[0002]

2. Description of the Related Art Ethylene-α-olefin non-conjugated diene copolymer compositions are excellent in various properties such as heat resistance, ozone resistance and weather resistance, and are used as solid rubbers, especially for seals such as glass run of automobiles and door seals. Widely used for members. However, when this glass run is mounted on an automobile, after a long period of time, a thin-walled seal lip (hereinafter referred to as a lip) that performs a sealing function while maintaining a sliding state with the contact member is opposite to the contact member. , That is, in the direction in which the sealing reaction force is weakened (hereinafter referred to as sag), which causes a problem that the glass flutters and the wind noise performance deteriorates.

In order to improve the sliding property of glass run, the rubber composition is subjected to a treatment such as a surface treatment coat. However, this treatment increases the cost and increases the cost of the surface treatment coat. There is a problem in that the slidability is deteriorated due to deterioration. Therefore, development of a hardened rubber that does not require a surface treatment coat or the like is desired.

[0004] In addition to the above-mentioned various properties, the rubber composition needs to be excellent in kneading workability, roll workability, extrusion moldability and the like in addition to the performance as a rubber.

[0005]

In order to solve the second problem described above, a rubber compound as disclosed in JP-A-10-195259 has been used. This rubber compound comprises an ethylene-α-olefin-non-conjugated diene copolymer having a low ethylene content (hereinafter referred to as copolymer-A) and an ethylene-α-olefin-non-conjugated diene having a high ethylene content. It is obtained by mixing (blending) with a copolymer (hereinafter, referred to as copolymer-B), has high hardness, is excellent in moldability, and is excellent in tensile strength, compression set and the like. The mixing ratio of the copolymers A and B (component A / component B) is 30/70 to 7 by weight.
It is known to be 0/30.

However, in order to solve the above two problems, it is desired to develop a rubber composition having better characteristics and better characteristics in a vehicle assembled state than the rubber composition comprising the copolymers A and B as described above. It is rare.

SUMMARY OF THE INVENTION The present invention has been made based on the above-mentioned problem, and it is an object of the present invention to provide a glass run extruded solid rubber having a high rigidity to improve the settability of a lip of a glass run and to solve the above-mentioned problem in an actual vehicle assembled state. An object of the present invention is to provide a rubber composition which can be appropriately evaluated and has excellent cold compression set, cold tensile set, shape retention and the like.

[0008]

According to the present invention, there is provided a rubber composition (sulfur vulcanization system) having an ethylene / propylene weight ratio of 70/70. A first EPDM having a high ethylene content and having crystallinity of 30 to 90/10, and a second EPDM having an ethylene / propylene weight ratio of 40/60 to 70/30.
(The ethylene content is relatively low) and the weight ratio of the first EPDM / second EPDM is 5/95 to 30/7.
The rubber compound prepared so as to be 0 is crosslinked. Incidentally, the ethylene crystal melting point of the first EPDM is 30 ° C. or more, and the JIS-
The hardness of A is 80 ± 5.

The invention according to claim 2 is characterized in that the rubber composition has a permanent compression set of 30% or less (a rate of change in the thickness of vulcanized rubber by a substitute evaluation test of the flapping control performance of glass in an actual vehicle). Tensile set (40% or less change in vulcanized rubber by sag evaluation test at glass run lip) is less than 40%, and shape change (unvulcanized rubber (rubber compound The thickness change rate of the material is 20% or less.

The first EPDM is a component that contributes to improvement in high hardness, kneading processability, and extrusion moldability. The second EPDM is a component that contributes to improvement in compression set and tensile strength at high and low temperatures and shape retention during extrusion molding. In addition, a crosslinking agent, an additive, a softening agent, and the like are added to the rubber compound as needed.

When the content of the first EPDM in the rubber compound is 5% or less, the rubber composition cannot maintain high hardness. Further, when the content of the first EPDM is 30% or more, shape retention during extrusion molding and, for example, rip resistance of glass run lip (cooling tensile permanent strain rate) deteriorate.

On the other hand, when the above-mentioned cooling-compressed permanent set exceeds 30%, and the cold-setting tensile set exceeds 40%, for example, the rip resistance of a glass run lip deteriorates. Further, when the shape change rate exceeds 20%, shape retention during extrusion molding is deteriorated.

According to the present invention, in a rubber composition such as solid rubber, high physical properties (hardness, compression set, etc.) can be ensured and set resistance (cooling compression set, cooling tensile set) can be ensured. Etc.) and extrudability (shape retention, extrudability, etc.) can be improved. For this reason, for example, in a sealing member such as a glass run used in an automobile, it is possible to improve various characteristics such as sealing properties, sliding properties, and sag resistance.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a rubber composition according to an embodiment of the present invention will be described with reference to the drawings.

In this embodiment, EPDM (ethylene-
Using propylene diene copolymer) to produce rubber compounds under various conditions, and examining the characteristics of the unvulcanized and vulcanized products made of each rubber compound, various characteristics (for example, cooling A rubber composition having excellent compression set, cold-set tensile set, and shape retention) was studied.

In the present embodiment, the weight ratio of ethylene to propylene (hereinafter referred to as the weight ratio of ethylene / the weight ratio of propylene) is first determined by polymerization according to a general method (for example, JP-A-10-195259). A first EPDM (hereinafter referred to as EPDM-1) having 70/30 to 90/10 ethylene / propylene and a high ethylene content and crystallinity is prepared. In addition, a second EPDM (hereinafter, referred to as EPDM-2) having a weight ratio of ethylene to propylene of 40/60 to 70/30 is produced. Thereafter, the EPD was prepared by a general method.
M-1, EPDM-2 and additives, etc.
The weight ratio of PDM-1 to EPDM-2 (hereinafter referred to as EPDM
-1 / weight ratio of EPDM-2) is obtained from 5/95 to 30/70, and the rubber composition is crosslinked to obtain a rubber composition.

The melting point of the crystalline portion (ethylene crystal melting point) of EPDM-1 is 30 ° C. or more in DSC measurement (differential scanning calorimetry).

Next, in order to examine the characteristics of the rubber composition prepared as described above, the EPDM (EPDM-1 and EPDM-2) was prepared by a general method.
Parts by weight are as shown in Table 1 below, using 170 parts by weight of SRF grade carbon black, 70 parts by weight of paraffinic oil, 20 parts by weight of heavy calcium carbonate, 3 parts by weight of zinc white, and 1 part by weight of stearic acid. As various weight ratio EPDM
Rubber compositions S1 to S4 of -1 / EPDM-2 were produced. In addition, for comparison with the above rubber compounds S1 to S4, various weight ratios of EPDM-1 /
EPDM-2 rubber compounds P1 to P3 were also prepared.

Each of the above rubber compounds S1 to S4, P1 to P
In Table 3, the weight ratio of ethylene / propylene in EPDM-1 and EPDM-2 and the weight ratio of ethylene / propylene in the rubber compound are shown in Tables 1 and 2, respectively.

[0020]

[Table 1]

[0021]

[Table 2]

Next, an additive comprising 1 part by weight of sulfur and 5 parts by weight in total of three kinds of accelerators (thiazole-based accelerator, thiuram-based accelerator, sulfenamide-based accelerator); 1, each rubber compound S1 to S4 shown in Table 2
Using P1 to P3, molded articles (test pieces) of the rubber composition were respectively produced by crosslinking by a general method.

The hardness (JIS-
A), a general compression set test (JIS-K626)
2) compression set (22 in a 70 ° C. atmosphere)
Time and 200 hours) to determine the normal physical properties. Also, under the conditions that can be correlated with the glass run mounted on the actual vehicle, that is, by the methods shown in the following (a) to (e), evaluation tests of set resistance (cooling compression set, cooling tension) Evaluation tests (permanent set, sag resistance at the glass run lip) and extrudability (characteristic evaluation test in the state of a compound (unvulcanized); shape retention, extrudability) were performed.

(A) Evaluation of Cooling Permanent Set for Cooling In order to carry out a substitute evaluation test of the flapping control performance of glass in an actual vehicle (the fluttering control performance of a window glass in a half-open to fully-closed state), first of all, Rubber compound S
1 to S4, P1 to P3 and a columnar shape (thickness 12.70)
Test pieces having a size of ± 0.13 mm and a diameter of 29.0 mm) were produced by vulcanization molding. Next, the test piece was fixed (set) to a jig for compression and 25% using a spacer.
The sample was compressed (compressed from both end faces of the test piece) and heat-treated in an atmosphere at a temperature of 80 ° C. for 48 hours, and then left in a compressed state at room temperature for 3 hours.

Thereafter, the test piece is removed from the jig.
To release the specimen, and the thickness H of the specimen ₁Was measured. Soshi
And the rate of change of the thickness of the test piece calculated by the following equation
(%) Is defined as the cooling permanent compression set, and each of the above rubber compounds
Permanent cooling and compression of test pieces consisting of S1 to S4 and P1 to P3
Each strain was evaluated. In the following equation, H
₀Is the thickness of the test piece before fixing to the jig, H_TwoIs a spacer
It shows the thickness of.

“Rate of change in thickness” = ((H ₀ −H ₁ ) / (H ₀ −H ₂ )) × 100 (1) (b) Evaluation of Tensile Permanent Strain of Cooling Set in Glass Run Lip In order to carry out a substitution evaluation test on the properties, first, each of the above rubber compounds S1 to S4, P1
Using the vulcanized molded sheet of P3 to P3, as shown in FIG.
Specimen 10 of IS standard dumbbell type 1 (2mm thickness)
Were prepared respectively. In the center of the test piece 10, two mark lines 11, 1 were separated by an interval L ₀ (40 mm).
Write 2.

Next, the test piece 10 was stretched in the directions of arrows A and B in the figure at elongation rates of 5, 10, and 20%, and was fixed to a jig, and was subjected to a heat treatment in an atmosphere at a temperature of 80 ° C. for 48 hours. After that, it was left at room temperature for 3 hours in the extended state.
Thereafter, the test piece 10 is removed from the jig to release the extension, and the length L ₁ between the marked lines 11 and 12 at each extension rate is determined.
Was measured respectively. Then, the length change rate (%) of the test piece 10 calculated by the following equation is defined as a cooling tension set, and the cooling tension of the test piece 10 composed of each of the rubber compounds S1 to S4 and P1 to P3 is set. Each of the evaluations of permanent set was performed. In the following formula, L ₀ indicates the length between the marked lines 11 and 12 of the test piece before being fixed to the jig (before being extended), and L ₂ indicates the length of the marked lines 11 and 12 of the test piece 10 at the time of extension. It shows the length between twelve.

“Length change rate” = (L ₁ −L ₀ ) / (L ₂ −L ₀ ) (2) (c) Evaluation of sag resistance Substitute evaluation of sag resistance in glass run lip portion In order to carry out the test, instead of producing an actual glass run, first, using each of the rubber compounds S1 to S4 and P1 to P3 described above, a substantially L having a body 21 and a lip 22 as shown in FIG. Each of the V-shaped vulcanized molded bodies 20 was produced. The molded body 20 is constructed by applying a load so as to deflect the lip portion 22, so that the built-in dimension L (dimension in a state of being pressed against a window glass in an actual vehicle; 5.8 mm)
(The state shown by the dotted line in FIG. 2), and the magnitude of the load N ₀ and the allowance F ₀ required for the compression were measured.

Next, the compact 20 was heated in an atmosphere of a temperature of 80 ° C. for 48 hours in a compressed state, and then allowed to cool at room temperature for 3 hours. Thereafter, the at immediately after and 30 minutes after releasing the compression to compress each of the up built with dimensions L shaped bodies was again measured size and flexure length F ₁ of the load N ₁ required for its compression. Then, by calculating the rate of change of load and the rate of change of deflection allowance by the following equations, the set resistance of the molded body 20 composed of each of the rubber compounds S1 to S4 and P1 to P3 was evaluated.

“Load change rate” = ((N ₀ −N ₁ ) / N ₀ ) × 100 (3) “Deflection allowance change rate” = ((F ₀ −F ₁ ) / F ₀ ) × 100 (4) (d) Evaluation of shape retention In order to conduct a substitute evaluation test of shape retention, circles made of unvulcanized rubber were first used by using each of the above rubber compounds S1 to S4 and P1 to P3. Columnar shaped body (thickness 12.7 ±
0.13 mm, diameter 29.0 mm). next,
In an atmosphere at a temperature of 100 ° C., a load of 1 kg was applied for 10 minutes from one end face direction of the molded body, and the thickness h ₁ of the molded body after releasing the load was measured. Then, using the thickness change rate calculated by the following equation as the shape change rate, the shape retention of the unvulcanized rubber composed of each of the rubber compounds S1 to S4 and P1 to P3 was evaluated. In the following equation, h
₀ indicates the thickness of the compact before applying a load.

“Rate of change in thickness” = ((h ₀ −h ₁ ) / h ₀ ) × 100 (5) (e) Evaluation of Extrusion Formability Substitution evaluation test for extrusion moldability (Garbe die evaluation test;
In order to carry out ASTM D2230), first, a molded article 30 having a cross-sectional garbage die shape was extruded with a predetermined die using each of the rubber compounds S1 to S4 and P1 to P3 as shown in FIG. The state of the swell, edge (reference numeral 31 in FIG. 3), skin, and corner (reference numeral 32 in FIG. 3) of the molded body 30 is changed from one stage (poor extrudability) to four stages (extrudability). Was good). The target of the extrudability was that the total of the evaluations was 14 or more.

The results of the evaluation tests of the rubber compounds S1 to S4 and P1 to P3 for the normal physical properties, set resistance, and extrudability measured as described above are shown in Tables 3 and 4 below. 4 are shown.

[0033]

[Table 3]

[0034]

[Table 4]

From the results shown in Table 4, it can be seen that when the rubber compound P1 was used, the set resistance and the extrudability could be improved, but the high hardness in the normal physical properties could not be maintained. . When the rubber compound P2 is used, it can be seen that high hardness in normal physical properties can be maintained, but sag resistance and extrudability deteriorate. In the case of using the rubber compound P3, it can be seen that high hardness in normal physical properties can be maintained, but set resistance and extrudability are extremely deteriorated.

On the other hand, from the results shown in Table 3, it was confirmed that, when the rubber compounds S1 to S4 were used, high physical properties in a normal state could be maintained, and good sag resistance and extrudability were obtained. Was.

Therefore, as in this embodiment, the weight ratio EP
DM-1 / EPDM-2 from 5/95 to 30/70,
The weight ratio of ethylene / propylene in EPDM-1 is 7
0/30 to 90/10, and a rubber composition in which the weight ratio of ethylene / propylene in EPDM-2 was 40/60 to 70/30.
Uncooled tensile permanent strain rate of 40% or less, shape change rate of 20%
Hereinafter, a rubber composition having a rubber hardness (JIS-A) of 80 ± 5 can be obtained.

Although the present invention has been described in detail with reference only to the specific examples described above, it will be apparent to those skilled in the art that various changes and modifications can be made within the technical idea of the present invention. It goes without saying that such variations and modifications belong to the scope of the claims.

[0039]

As described above, according to the present invention, in a rubber composition such as a solid rubber, high normal physical properties (hardness, compression set, etc.) can be ensured and set resistance (cooling compression set) can be ensured. Strain rate, cold standing tensile permanent strain rate, etc.) and extrudability (shape retention, extrudability, etc.) can be improved. For this reason, for example, in a sealing member such as a glass run used in an automobile, a sealing property, a sliding property,
Various characteristics such as set resistance can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic view of a test piece used for evaluation of a standing tension tensile strain.

FIG. 2 is a schematic view of a molded article used for evaluation of sag resistance.

FIG. 3 is a schematic view of a molded article used for evaluation of extrusion moldability.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Test piece 20, 30 ... Molded body 11, 12 ... Mark line 22 ... Lip part 31 ... Edge 32 ... Corner

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroshi Togami 330F, Naganuma-cho, Inage-ku, Chiba-shi, Chiba F-term (reference) 4F070 AA16 AC04 AC05 AC14 AC16 AC94 AE08 GA06 GC01 4J002 BB151 BB152 GN00

Claims (2)

[Claims] An ethylene / propylene weight ratio of 70 /
A first EPDM having an ethylene crystal melting point of 30 to 90/10 and an ethylene crystal melting point of 30 ° C. or higher, and a weight ratio of ethylene / propylene of 40;
/ 60-70 / 30, and the weight ratio of the first EPDM / second EPDM is 5 / 95-3.
The rubber compound prepared to be 0/70 was cross-linked,
A rubber composition having a hardness of IS-A of 80 ± 5. 2. The rubber compound has a shape change rate of 20% or less, and the rubber compound is cross-linked to reduce the permanent compression set to 30% or less and the tensile set to 40% or less. The rubber composition according to claim 1, wherein