JP2003171489A - Rubber foam for sealing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber foamed material for sealing, capable of shortening a time for vulcanization and foaming, by forming a mixture into a thin shape, and capable of being formed into such a rubber foamed material that has a heavy thickness. <P>SOLUTION: This rubber foamed material for sealing is obtained by preparing a mixture containing an ethylene-propylene-diene rubber in an amount of ≥25 wt.%, then subjecting the mixture to the vulcanization and foaming, wherein the ethylene-propylene-diene rubber has a weight-average molecular weight (Mw) of 100,000-500,000 and a ratio of the weight-average molecular weight (Mw) to a number-average molecular weight (Mn) (Mw/Mn) of ≥10, and the rubber foamed material has a foam density of ≤0.15 g/cm<SP>3</SP>and an expansion ratio of ≥2.5 in the direction in which the material rises up. <P>COPYRIGHT: (C)2003,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] TECHNICAL FIELD The present invention relates to a rubber foam for sealing.
Suitable as sealant for body, more specifically for various industrial products
The present invention relates to a rubber foam for sealing used. [0002] 2. Description of the Related Art Conventionally, for example, automobiles, electric
Products, housing products, and other industrial products
A sealing material for sealing is used. As such a sealing material, for example,
Tylene / propylene / diene rubber, vulcanizing agent and foaming agent
Obtained by vulcanizing and foaming an admixture containing
Foam is excellent in weather resistance, cold resistance, heat resistance, chemical resistance etc.
It is widely used because of its low cost. [0004] However, general-purpose etchants
Large thickness using ren-propylene-diene rubber
When trying to obtain a rubber foam, for example,
It is necessary to extrude into a sheet shape and perform vulcanization and foaming.
When foaming, apply heat evenly to the inside of the thick sheet
Must take a lot of time,
This causes a problem that the efficiency is significantly reduced. The present invention has been made in view of such a problem.
The purpose is to thin the mixture.
Molding and shortening the vulcanization and foaming time while reducing the thickness.
Sealing rubber that can be obtained as a large rubber foam
To provide a foam. [0006] SUMMARY OF THE INVENTION In order to achieve the above object,
The rubber foam for sealing of the present invention has a weight average molecular weight
(Mw) is 100,000 to 500,000, and number average molecular weight
Ratio of weight average molecular weight (Mw) to (Mn) (Mw /
Ethylene / propylene / diene rubber having Mn) of 10 or more
Ethylene propylene diene containing at least 25% by weight of
Contains foam rubber and foam density 0.15g / cm³Less than
And the expansion ratio in the height direction is 2.5 times or more.
It is characterized by. [0007] BEST MODE FOR CARRYING OUT THE INVENTION The rubber foam for sealing of the present invention comprises:
Ethylene propylene diene rubber (hereinafter referred to as EPDM)
I do. ). [0008] Ethylene / propylene used in the present invention
・ Diene rubber (hereinafter referred to as EPDM)
Obtained by copolymerization of ethylene, propylene and dienes.
Rubber, which is further added to ethylene-propylene copolymer.
To introduce unsaturated bonds by copolymerizing dienes
Thus, vulcanization with a vulcanizing agent is enabled. The diene is not particularly limited,
For example, ethylidene norbornene, 1,4-hexadiene
And dicyclopentadiene are used. [0010] The rubber foam for sealing of the present invention comprises:
Weight average molecular weight (Mw) of 100,000 to 500,000, preferably
Is 200,000 to 400,000, and the number average molecular weight (M
n) to the weight average molecular weight (Mw) (Mw / M
n) (hereinafter simply referred to as ratio (Mw / Mn)) of 10 or less
Above, preferably 12 or more, more preferably 15 to
25 ethylene-propylene-diene rubber
It is assumed to be dispersive EPDM. ). [0011] The weight average molecular weight (M
If w) is lower than this, foaming does not occur much in the height direction, and
To produce a thick foam, even inside a thick sheet
It takes time to apply heat evenly, and the productivity decreases.
On the other hand, if it is higher, the production of EPDM itself
And it is difficult to obtain as a commercial product. So like this
EPDM with a weight average molecular weight (Mw) in a wide range
By compounding, foaming in the height direction is high, so thick foaming
When producing foam, a thin sheet is sufficient and heat is evenly distributed inside.
Time can be reduced and productivity can be improved.
it can. The weight-average molecular weight (Mw) is a known value.
Method, for example, gel permeation chromatography
The molecular weight distribution was measured by chromatography (GPC).
From the measurement results of
The average molecular weight (Mw) can be determined. [0013] The highly dispersible EPDM is
In the range of the weight average molecular weight (Mw), the ratio (Mw)
/ Mn) is 10 or more. The ratio (Mw / Mn)
If it is lower than this, it does not foam much in the height direction and thick foam
When trying to produce a body, evenly inside the thick sheet
It takes time to apply heat and productivity is reduced. The ratio (Mw / Mn) is determined by a known method.
For example, gel permeation chromatography
The molecular weight distribution is measured by fee (GPC) and the measurement is performed.
From the results, the weight average molecule as standard polystyrene conversion
Weight (Mw) and number average molecular weight (Mn)
It can be obtained by calculating the ratio (Mw / Mn).
Wear. Further, the EPDM ratio (Mw / Mn) is adjusted.
For this purpose, a known method is appropriately used. For example,
Coordination anion polymerization of len, propylene and dienes
The type of Ziegler catalyst and its co-catalyst
To an arbitrary ratio (Mw / Mn) by selecting
be able to. EPDs with different ratios (Mw / Mn)
For M, commercially available ones can be used if necessary.
it can. In the rubber foam for sealing of the present invention,
Represents the weight average molecular weight (Mw) and the ratio in such a range.
By blending (Mw / Mn) highly dispersible EPDM,
Even if the admixture described later is molded thinly, it will produce a thick rubber.
A foam can be obtained and the vulcanization time can be shortened.
Thus, the production efficiency can be improved. Incidentally, such highly dispersible EPDM is particularly
But not limited to Mooney viscosity (ML_{1 + 4}, 125
C) is from 20 to 80, and the diene content is from 2.5 to 11.
5% by weight and ethylene content is 50-70%
Preferably, the weight average molecular weight (Mw) and the ratio (M
If w / Mn) is within the above range, various types of
One or two or more can be selected from
Can be. The compounding amount of the highly dispersible EPDM is EP
It is at least 25% by weight based on the total amount of DM. High dispersibility
If the blending amount of EPDM is lower than this, too much in the height direction
When trying to produce thick foam without foaming,
It takes time to apply heat evenly to the inside of the
Decreases. That is, in the rubber foam for sealing of the present invention,
The amount of highly dispersible EPDM is 25% by weight or more.
If the total amount of EPDM is
Is 100% by weight (ie all highly disperse EPDM)
And the highly dispersible EPDM is 100% by weight.
% (Ie, highly disperse EPDM and other EPDM
(Hereinafter, referred to as low-dispersion EPDM)).
You may. The amount of the highly dispersible EPDM is preferably
Is 30% by weight or more, and more preferably 30 to 80 weights.
%. In addition, low dispersibility EP blended in that case
DM has, for example, a weight average molecular weight (Mw) of 1 × 1
0⁵~ 5 × 10⁵, Preferably 2 × 10⁵~ 4 × 10
⁵And the ratio (Mw / Mn) is less than 10, preferably
More preferably, it is less than 4.5, more preferably 3-4.
Less than 75% by weight of such low dispersibility EPDM is preferred.
Or less than 70% by weight, more preferably 20 to 7% by weight.
By mixing at 0% by weight, the kneading processability is improved.
Can be planned. Incidentally, such a low-dispersion EPDM is particularly
But not limited to Mooney viscosity (ML_{1 + 4}, 125
C) is from 20 to 80, and the diene content is from 2.5 to 11.
5% by weight and ethylene content is 50-70%
Preferably, from various kinds, one kind or two kinds
More than one kind can be appropriately selected and used. The rubber foam for sealing of the present invention is
A curing agent and a foaming agent are blended with such EPDM, and vulcanization is performed.
It can be obtained by sulfuric foaming. The vulcanizing agent is not particularly limited.
For example, sulfur, sulfur compounds, selenium, magnesium oxide
System, lead monoxide, zinc oxide, organic peroxides, polyamines
, Oximes (eg, p-quinone dioxime, p,
p'-dibenzoylquinone dioxime), nitroso
Compounds (eg, p-dinitrosobenzine, etc.), trees
Fats (eg, alkylphenol-formaldehyde)
Resin, melamine-formaldehyde condensate, etc.)
Monium salts (eg, ammonium benzoate, etc.)
Which is used. One or more of these vulcanizing agents
Can be appropriately selected and used, and the obtained rubber foam
From the viewpoint of the physical properties resulting from the vulcanizability of, preferably,
Sulfur and sulfur compounds, more preferably sulfur
It is. The mixing ratio of the vulcanizing agent depends on the type of vulcanizing agent.
Since the sulfur efficiency is different, it may be appropriately selected, for example,
For sulfur and sulfur compounds, 100 parts by weight of EPDM
0.1 to 10 parts by weight, preferably 0.5 to 3 parts by weight
Department. There is no particular limitation on the foaming agent.
However, for example, an inorganic foaming agent or an organic foaming agent is used.
You. As the inorganic blowing agent, for example, ammonium carbonate
, Ammonium bicarbonate, sodium bicarbonate, nitrous acid
Ammonium, sodium borohydride, azides
Which is used. Also, as an organic foaming agent, for example,
For example, N-nitroso compounds (N, N'-dinitrosopene)
Tamethylenetetramine, N, N'-dimethyl-N, N '
-Dinitrosoterephthalamide, etc.), azo compounds
(For example, azobisisobutyronitrile, azodicarbo
Acid amide, barium azodicarboxylate, etc.),
Fluorinated alkanes (eg, trichloromonofluorometa
, Dichloromonofluoromethane, etc.), hydrazine type
Compounds (eg, paratoluenesulfonyl hydrazide,
Diphenylsulfone-3,3'-disulfonylhydrazide
4,4'-oxybis (benzenesulfonylhydra
Zide), allylbis (sulfonylhydrazide), etc.),
Semicarbazide compounds (for example, p-toluylenesul
Honyl semicarbazide, 4,4'-oxybis (benze
Sulfonylsemicarbazide)), triazole
Compounds (for example, 5-morpholyl-1,2,3,4-thio
Attriazole and the like are used. The foaming agent is a heat-expandable substance.
Are heat-expandable fine particles encapsulated in microcapsules
May be used. As such thermally expandable fine particles,
For example, microspheres (trade name, manufactured by Matsumoto Yushi Co., Ltd.)
Any commercially available product may be used. One or more of these foaming agents are suitable.
The rubber foam can be selected and used as appropriate.
From the viewpoint of the physical properties resulting from the foaming property, preferably, N-
An organic foaming agent such as a nitroso compound is used. Ma
Further, the compounding ratio of the foaming agent is, for example, EPDM 100 weight
Parts by weight, preferably 0.1 to 100 parts by weight, preferably 1 to 100 parts by weight.
50 parts by weight. In the vulcanization and foaming, vulcanization is promoted.
Vulcanization accelerator to promote the process and foaming aid to ensure good foaming
It is preferable to mix agents and the like. As the vulcanization accelerator, for example, dithiocar
Bamic acids (eg, dimethyldithiocarbamate
Lium, sodium diethyldithiocarbamate,
Zinc tildithiocarbamate, diethyldithiocarbami
Zincate, etc.), thiazoles (eg, 2-mercap
Tobenzothiazole, dibenzothiazyl disulfide
Guanidines (eg, diphenylguanidine,
Di-o-tolylguanidine, etc.), sulfenamides
(For example, benzothiazyl-2-diethylsulfena
Mido, N-cyclohexyl-2-benzothiazyl sulf
Enamide, etc.), thiurams (eg, tetramethyl
Thiuram monosulfide, tetramethylthiuram disul
And xanthogenic acids (eg, isopropyl
Luxanthogen sodium, isopropyl xanthogen
Zincate), aldehyde ammonias (for example,
Cetaldehyde ammonia, hexamenthylene tetrami
Aldehyde amines (eg, n-butylamine)
Rudehydraniline, butyraldehyde monobutylamine
Thioureas (eg, diethylthiourea,
For example, trimethylthiourea). This
Such vulcanization accelerators are appropriately selected from one or more kinds.
Can be used, for example, from the viewpoint of vulcanization rate, etc.
Combination use of dithiocarbamic acids and thiazoles
Is preferred. The compounding ratio of the vulcanization accelerator is blue-resistant.
For example, EPDM 10
0.1 to 10 parts by weight, preferably 0 part by weight,
1 to 5 parts by weight. Incidentally, contrary to the vulcanization accelerator, the molding processability
For the purpose of, for example, controlling organic acids (for example,
Water phthalic acid, benzoic acid, salicylic acid, etc.) and amines
(For example, N-nitroso-diphenylamine, N-nit
Vulcanization such as roso-phenyl-β-naphthylamine)
A retarder may optionally be included. Examples of the foaming aid include urea-based compounds
Products, salicylic acid compounds, benzoic acid compounds, etc.
Can be These foaming assistants may be used alone or in combination of two or more.
Can be selected and used, preferably for vulcanization.
From the viewpoint of low impact and low cost, urea
A system compound is used. The mixing ratio of the foaming aid is
For example, 1 to 30 parts by weight based on 100 parts by weight of EPDM
Parts, preferably 2 to 15 parts by weight. Further, in this vulcanization and foaming, for example,
Stabilizers, lubricants, reinforcements, fillers and softeners,
If necessary, for example, plasticizer, anti-aging agent, acid
Antioxidants, pigments, colorants, fungicides and flame retardants
Known additives may be appropriately blended. Examples of the stabilizer include zinc oxide.
It is preferably used and its compounding amount is EPDM 100 weight
1 to 10 parts by weight, preferably 3 to 5 parts by weight
Department. [0034] Examples of the lubricant include stearic acid and sulfuric acid.
Esters etc. are used, the amount of which is EPDM
0.5 to 5 parts by weight, preferably 100 parts by weight
Is 1 to 3 parts by weight. As a reinforcing material, for example, carbon black
And the like are preferably used.
5 to 50 parts by weight, preferably 1 to 100 parts by weight
0 to 20 parts by weight. The filler is not particularly limited.
For example, calcium carbonate, aluminum hydroxide, mug carbonate
Nesium, magnesium hydroxide, calcium oxide, silica
Acid and its salts, clay, talc, mica powder, bentona
, Silica, alumina, aluminum silicate, aluminum
Cetylene black, aluminum powder and the like are used.
One or more of these fillers are appropriately selected for use.
Preferably, calcium carbonate is used.
It is. The amount of the filler is based on 100 parts by weight of EPDM.
80 to 200 parts by weight, preferably 100 to 180 parts by weight.
Parts by weight. The softener is not particularly limited.
However, for example, drying oils and animal and vegetable oils (eg, paraffin
(Paraffin oil, etc.), waxes, naphthe
, Aromas, linseed oil, etc.), asphalt, stone
Oil-based oils, low molecular weight polymers, organic acid esters
(E.g. phthalates, phosphates, higher fats
Fatty acid esters, alkylsulfonic acid esters, etc.)
A tackifier or the like is used. These softeners may be used alone or
Can be used by appropriately selecting two or more kinds.
Is asphalt, petroleum-based process oil, paraffin
An oil-based process oil is used. The amount of the softener is
20 to 250 parts by weight based on 100 parts by weight of EPDM,
Preferably, it is 50 to 200 parts by weight. Then, the vulcanization foaming is carried out, for example, first in EP
DM and known additives are appropriately selected and blended.
Using a kneader, mixer or mixing roll
The mixture is prepared by kneading the mixture. What
In this kneading, heating may be appropriately performed. Next
In addition, the vulcanizing agent, blowing agent, vulcanization acceleration
Ingredients and foaming aids are appropriately selected and blended.
After further kneading using
Just do it. More specifically, such vulcanized foam is
There is no particular limitation, and known methods can be used.
For example, the mixture can be
May be molded into a sheet or the like and vulcanized and foamed.
Or, by injection molding or press molding, for example,
It may be formed into a complex shape such as a convex and vulcanized and foamed. The heating temperature in such vulcanization and foaming is as follows.
The degree is, for example, the curing start temperature of the compounded vulcanizing agent,
Selected as appropriate depending on the foaming temperature of the foaming agent to be combined.
However, for example, 450 ° C. or less, preferably 100 to 3
50 ° C. By such vulcanization and foaming, the admixture is softened.
While the foaming agent expands, vulcanization while forming a foamed structure
Proceeds to form a desired rubber foam. What
In such vulcanization and foaming, vulcanization and foaming are performed.
These steps may be performed sequentially at different temperature conditions.
In addition, for the purpose of adjusting the expansion ratio, etc.
May be. Then, according to the present invention thus obtained,
The rubber foam for sealing has a foam density (weight of foam)
(G) / volume of foam (g / cm³)) Is 0.15 g /
cm ³Or less, preferably, 0.06 to 0.12 g / cm
³And the height direction (standing when foaming the rubber foam)
Expansion ratio (thickness of rubber foam after foaming)
2.5 times or more of the mixture before foaming), preferably
2.8 to 4.5 times. The expansion ratio in the height direction is
EPDM composition, blending ratio of blowing agent, vulcanized foam
It can be adjusted by time and temperature, etc.
It can be obtained by adjusting the expansion ratio etc.
Cell size and cell morphology of the rubber foam (closed cell
Or open cells and their proportions)
Can be The foam density is 0.15 g / cm³Exceeds
And the repulsive stress during compression increases, making it difficult to compress,
When the expansion ratio in the height direction is less than 2.5 times,
If you are trying to obtain a good foam (for example, 40 mm or more)
Thicker sheet is required,
On the one hand, it takes time to apply heat, and productivity is reduced. The form of the cell of the obtained rubber foam is
Can be only closed cells, only open cells, or even
Closed cells and open cells may be mixed. The rubber foam for sealing of the present invention is
In such vulcanization foam, a rubber foam having a large thickness
In the case of obtaining
Even if the product is not formed into a thick sheet, it can be formed into a thin sheet
Can be molded to obtain thick rubber foam
You. Therefore, during vulcanization and foaming, for example,
When it is molded into a shape, heat is evenly applied to the inside.
Requires much time and production efficiency
Notably reduced, but without such defects, vulcanized foam
A rubber foam with a large thickness while shortening the time
And can be obtained with good production efficiency. More specifically, for example, the mixture is
If it is formed into a sheet of 5 to 10 mm and vulcanized and foamed,
A rubber foam having a thickness of 15 to 40 mm can be obtained. Therefore, the rubber foam for sealing of the present invention
Is dust-proof, heat-insulated, sound-proof, vibration-proof, shock-absorbing, watertight and airtight
For example, dust-proofing materials, heat-insulating materials, soundproofing materials,
As a vibration material, cushioning material, filler, waterproof material, etc.,
When a thick sealing material is required,
Price, can be provided with sealing materials for various industrial products
And can be suitably used. In the above description, “vulcanization” means
Synonymous with "crosslinking", not limited to bridging with sulfur
It is used as [0049] The following examples and comparative examples illustrate the present invention.
As will be described more specifically, the present invention is not limited to Examples and
The present invention is not limited to the comparative examples. Examples and Comparative Examples In the formulation shown in Table 1, first, various weight average
EPDM of molecular weight (Mw) and ratio (Mw / Mn), oxidation
Zinc, powdered stearic acid, carbon black, calcium carbonate
With asium, asphalt and paraffinic process oils
And kneading it using a pressure kneader.
A mixture A was prepared. Next, the mixture A was further mixed with sulfur,
Zinc tildithiocarbamate, dimethyldithiocarbamic
Zincate, 2-mercaptobenzothiazole, dinitro
Sopentamethylenetetramine and urea foaming aid
And kneading the mixture using a mixing roll.
Thus, the mixture B was prepared. Then, this mixture B was used in an extruder.
And extruded into 5mm thick sheet
By vulcanizing and foaming for 30 minutes with
A rubber foam was obtained. The obtained Examples 1 and 2 and Comparative Examples 1 to 3
Weight (g) and volume (cm) of the rubber foam³) Measure
And foam density (g / cm³) And foaming
The foaming ratio in the height direction was determined from the thickness before and after. as a result
Are shown in Table 1. [0054] [Table 1]The details of EPDM in Table 1 are shown below. EPDM1: diene: ethylidene norvol
Nene and diene content: 6% by weight, Mooney viscosity (ML
_{1 + 4}, 125 ° C): 25, ethylene content: 53%,
Weight average molecular weight (Mw): 2.6 × 10⁵, Ratio (Mw /
Mn): 3.1 EPDM2: diene: ethylidene norbornene, diene
Content: 3% by weight, Mooney viscosity (ML_{1 + 4}, 125
° C): 20, ethylene content: 67%, weight average molecular weight
(Mw): 2.4 × 10⁵, Ratio (Mw / Mn): 15.
8 EPDM3: Diene: Ethylidene norbornene, Diene
Content: 5.5% by weight, Mooney viscosity (ML_{1 + 4}, 12
5 ° C): 80, ethylene content: 55%, weight average molecule
Amount (Mw): 3.8 × 10⁵, Ratio (Mw / Mn): 2.
8 As is clear from Table 1, in Comparative Example 1, the ratio (Mw / M
n) Since only EPDM with 10 or less is used,
Foam density of 0.15 (g / cm³) Less than, but high
The expansion ratio in the vertical direction is less than 2.5 times. In Comparative Example 2, the ratio (Mw / Mn) was
The compounding amount of EPDM of 10 or more is less than 25% by weight.
The foam density is 0.15 (g / cm³) Is
However, the expansion ratio in the height direction is less than 2.5 times. Further, in Comparative Example 3, the ratio (Mw / Mn)
Is 10 or less, and the weight average molecular weight is
Low (Mw = 2.6 × 10⁵) And high (Mw =
3.8 × 10⁵) And height by blending
The expansion ratio in the direction is 2.5 times or more.
On the other hand, when the foam density is 0.15 (g / cm³) Bigger
It's getting worse. On the other hand, in Examples 1 and 2, the ratio (Mw / M
n) EPDM of 10 or more is blended in an amount of 25% by weight or more.
The foam density is 0.15 (g / cm³Below)
With a foaming ratio of 2.5 times or more in the height direction
are doing. [0059] As described above, the sealing rubber according to the present invention is used.
Foam has a large expansion ratio in the height direction,
Even when obtaining a large rubber foam,
Is to form the mixture thinly and heat and foam it in a short time.
Can be. As a result, it is produced as a thick rubber foam.
It can be obtained with good production efficiency.

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Claims (1)

Claims: 1. A weight average molecular weight (Mw) of 100,000 to 50.
An ethylene-propylene-diene rubber containing 25% by weight or more of an ethylene-propylene-diene rubber having a weight-average molecular weight (Mw) to number-average molecular weight (Mn) ratio (Mw / Mn) of 10 or more. The foam density is 0.15 g / cm ³ or less, and the foaming ratio in the height direction is 2.5 times or more,
Rubber foam for sealing.