JPH08100125A - Silicone rubber composition - Google Patents

Abstract

PURPOSE: To obtain the subject composition having a low crepe hardening properties and little variation in William plasticity by compounding an organopolysiloxane with a hydrophobic aerosol silica having a large amount of absorbed carbon and a low-molecular weight silicon compound containing silanol. CONSTITUTION: This rubber composition is obtained by compounding (A) 100 pts.wt. of organopolysiloxane of the formula R<1> n SiO(4-n)/2 (R<1> is a monovalent hydrocarbon; (n) is a positive number of 1.98-2.02) and terminal non-blocked ratio preferably of <=20mol.%, (B) 10-70 pts.wt., preferably 20-60 pts.wt. of hydrophobic aerosol silica having >=2wt.% of absorbed carbon and hydrophobicity of >=50vol.% and (C) 0-3 pts.wt., preferably 0.1-3 pts.wt. of a low-molecular weight silicon compound containing a silanol preferably of formula I (R<2> is methyl, phenyl, 3,3,3-trifluoropropyl or trimethylsiloxy) and having an Si-atom number of 1-10 (e.g. a compound of formula II formula III, etc.). Further, variation in William plasticity of the composition is preferably <=50.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention has a low crepe hardening property (plasticity reversion), so that even if a silicone rubber composition is stored for a long time before being added with a vulcanizing agent (U stock), it can be used in Williams. The present invention relates to a silicone rubber composition having a small change in plasticity.

[0002]

2. Description of the Related Art Generally, since silicone rubber is excellent in weather resistance, durability, heat resistance, physiological inertness, coloring property, etc., it is used for building materials, electric / electronic parts, office equipment parts. It is used in various fields such as automobile parts and medical equipment. In this case, the silicone rubber is
Since the strength of the silicone polymer itself is small,
A mixture of reinforcing silica such as fumed silica and precipitated silica is usually used. This high-strength silicone rubber can be obtained by adding a relatively large amount of reinforcing silica to a silicone polymer. However, if a large amount of reinforcing silica is added, the resulting silicone rubber composition will have too high a Williams plasticity, On the contrary, it is inferior in workability,
It reduces the economic efficiency during processing. Further, when the reinforcing silica is highly filled, the crepe hardening property of the silicone rubber composition becomes very high. Therefore, when it is used after being stored in the U stock state for transportation and storage, sufficient rough kneading is required. Or even worse, it may cause crepe hardening that makes even rough kneading impossible. This crepe hardening can be suppressed and improved by adding a large amount of a dispersant, but when a large amount of a dispersant is added, the stickiness of the surface of the silicone rubber composition increases, the roll adhesion becomes large, and the workability deteriorates, Further, it deteriorates the mechanical strength after curing.

The present invention has been made in view of the above circumstances.
It is an object of the present invention to provide a silicone rubber composition having a low crepe hardening property and a small change in Williams plasticity even when stored in a U-stock state for a long period of time.

[0004]

Means and Action for Solving the Problems The present inventors have
As a result of various studies aimed at developing the above-mentioned object and developing a silicone rubber composition having a small change in Williams plasticity even when stored in a U-stock state for a long period of time, as a result, the silicone polymer was surface-treated with an organic silicon and adsorbed. By incorporating a hydrophobic fumed silica having a large carbon adsorption amount of 2% by weight or more and a hydrophobicity of 50% by volume or more, the crepe hardening property of the silicone rubber composition can be suppressed to a low level, The present inventors have found that it is possible to reduce the change in Williams plasticity, and have completed the present invention.

That is, the present invention provides (A) the following average composition formula (1) R ¹ _n SiO _{(4-n) / 2} (1) (wherein R ¹ is the same or different and is unsubstituted or substituted 1 100 parts by weight of an organopolysiloxane represented by a valent hydrocarbon group, n is a positive number of 1.98 to 2.02, and (B) the amount of adsorbed carbon is 2% by weight or more and the degree of hydrophobicity is 50% by volume. Silicone rubber composition comprising 10 to 70 parts by weight of the above hydrophobic fumed silica and 0 to 3 parts by weight of (C) a silanol group-containing low-polymerization silicon compound having a silicon atom number of 1 to 10 Provide things.

The present invention will be described in more detail below. The silicone rubber composition of the present invention contains (A) organopolysiloxane and (B) hydrophobic fumed silica as essential components, and more preferably (C). It contains a silanol group-containing low-polymerization silicon compound.

Here, the organopolysiloxane as the component (A) is represented by the following average composition formula (1) R ¹ _n SiO _{(4-n) / 2} (1).

In this formula, R ¹ is an alkyl group such as a methyl group, an ethyl group, a propyl group or a butyl group, a cycloalkyl group such as a cyclohexyl group, an alkenyl group such as a vinyl group, an allyl group, a butenyl group or a hexenyl group, From a phenyl group, an aryl group such as a tolyl group, or a chloromethyl group in which some or all of the carbon atoms bonded to the carbon atoms of these groups are substituted with a halogen atom, a cyano group, a trifluoropropyl group, a cyanoethyl group, etc. Selected,
Identical or different carbon number 1-10, preferably carbon number 1-
8 is an unsubstituted or substituted monovalent hydrocarbon group. Also, n
Is a positive number from 1.98 to 2.02, and the end of the molecular chain is blocked with a trimethylsiloxy group, a dimethylphenylsiloxy group, a dimethylvinylsiloxy group, a trivinylsiloxy group, or the like. In this case, 0.001 of R ¹
5 mol% is preferably an alkenyl group.

It is desirable that the end of this organopolysiloxane is 100% blocked with a group such as the above-mentioned trialkylsiloxy group. In some cases, the terminal group may be terminated by silanol due to mixed water. In the present invention, it is preferable to use, as the organopolysiloxane, those whose unblocked ends terminated by this silanol group are 20 mol% or less, preferably 10 mol% or less. Use of an organopolysiloxane having a terminal unblocked ratio of more than 20 mol% tends to increase the crepe hardening property, resulting in the disadvantage that the processability of the silicone rubber composition is deteriorated. In addition, such an organopolysiloxane having a high end-blocking rate is disclosed in Japanese Examined Patent Publication No. 61-1.
It can be synthesized by a known method described in Japanese Patent Publication No. 2931, Japanese Patent Publication No. 62-20194 and the like.

As a method for measuring the unblocked ratio of the organopolysiloxane, for example, the organopolysiloxane is dissolved in a soluble solvent, and if the polymer does not contain a phenyl group, dimethylphenylchlorosilane is reacted and then the solvent and the Method to measure by removing excess silane, then pyrolyzing the polymer reacted with chlorosilane with alkali, and detecting the phenyl group reacted with the uncapped terminal terminated with silanol as benzene by gas chromatography analysis of the decomposed product. Is adopted.

The organopolysiloxane as the component (A) may have a viscosity at 25 ° C. of 1,000 cs or more, but is usually 100,000 to 10,000.
It is preferable that it is of 10,000 cs. Degree of polymerization is 30
It may be 0 or more, but usually 2,000 to 100,0
00, preferably 5,000 to 10,000
0.

The organopolysiloxane of this kind is usually obtained by (co) hydrolyzing and condensing one or more selected organohalogenosilanes, or cyclic polysiloxane (trimer or tetramer of siloxane). Body) and the like) can be obtained by ring-opening polymerization using an alkaline or acidic catalyst. This is basically a linear diorganopolysiloxane, but it has two different molecular structures. It may be a mixture of the above.

Next, the hydrophobic fumed silica as the component (B) is obtained by treating the fumed silica with an organic silicon compound, and the adsorbed carbon amount is 2% by weight or more and the hydrophobicity is 50%. Use the above.

Examples of the organic silicon compound for surface-treating the fumed silica include dimethyldichlorosilane, dimethylsiloxane, hexamethyldisilazane, hexamethylcyclotrisiloxane and octamethylcyclotetrasiloxane. A known method can be adopted as the surface treatment method, but in order to achieve the adsorbed carbon amount and the degree of hydrophobicity, a fluid reaction tank, an autoclave, a batch type mixing vessel, etc. are used, and a fluid reaction (gas-solid reaction) is performed. ), Pressurized high temperature reaction, reflux type wet treatment reaction and the like are preferably employed.

In the present invention, the hydrophobic silica has an adsorbed carbon amount of 2% by weight or more and a hydrophobicity of 50% by volume.
It is necessary to use the above. That is, the crepe hardening property of the silicone rubber is kept low by blending the silicone raw rubber with 2% by weight or more of the carbon adsorbed after the surface treatment with the organic silicon compound and a large amount of the carbon-adsorbed amount of the hydrophobic fumed silica. 2% by weight of adsorbed carbon has little improvement in crepe hardening at the end, and the change in Williams plasticity in U stock is large, so 2% by weight of adsorbed carbon by surface treatment is obtained.
It is necessary to do above. The upper limit of the surface-treated and adsorbed carbon is not particularly limited, but if it exceeds 10% by weight, stable production of treated silica is difficult.

The amount of carbon adsorbed after the surface treatment is an index showing how much the silica surface is treated, and the degree of hydrophobicity is one of the indicators of the hydrophobicity of the treated hydrophobic silica. In the hydrophobic fumed silica of the present invention,
In the hydrophobic treatment of the silica surface, both the amount of carbon, which represents the amount of treatment, and the degree of hydrophobicity, which represents the strength of treatment, must show sufficient hydrophobicity. Here, the degree of hydrophobization is measured by titrating methanol so that silica can be completely wetted by dropping methanol into water, and it is generally expressed by the volume% of methanol at this time, which is commonly called "M value". (Reference Polymer Digest 1983.3, p92
〜101). If the degree of hydrophobicity is less than 50%, the treating agent is liberated from the silica surface during compounding of the silicone rubber and is insufficient for improving the crepe hardening property, so it is necessary to set it to 50% or more. The upper limit is not particularly limited, but it is difficult to manufacture hydrophobic fumed silica having a hydrophobicity of more than 80%.

A combustion method is adopted as a method for measuring the amount of adsorbed carbon. In this method, the sample is burned in an oxygen stream to oxidize the contained carbon into carbon dioxide gas, and this is completely buretted together with oxygen. After sending it in and measuring its total capacity,
After passing through the alkaline solution to completely absorb the carbon dioxide gas, it is returned to the original burette again, and the carbon amount can be determined from the difference in capacity.

The incorporation of fumed silica into silicone rubber is the most effective means for improving the mechanical strength of silicone rubber, but for this purpose the hydrophobic fumed silica has a specific surface area of 100 m ² / It is preferably g or more.
However, if it exceeds 300 m ² / g, the Williams plasticity of the compounded rubber composition may become abnormally high and the crepe hardening property may become large.
It is preferably 0 m ² / g. Preferably 120-
It is 250 m ² / g.

Such surface-treated fumed hydrophobic silica is commercially available. For example, Tohoku Corporation's Reolosil GT20, Reorosil DM30S, Reorosil MT30, Degussa AG's Aerosil R202, Aerosil RY202, Aerosil RY200, etc. There is. The amount of the silica powder added is 10 with respect to 100 parts by weight of the organopolysiloxane as the component (A).
If it is less than part by weight, it is too small to obtain a sufficient reinforcing effect,
If the amount is more than 70 parts by weight, the mechanical strength of the silicone rubber obtained after curing will be rather deteriorated, and the Williams plasticity of the silicone rubber composition will be too high, making it rather difficult to process. It is necessary to be a part, and a more preferable range is 20 to 6.
0 parts by weight.

The silanol group-containing low degree of polymerization silicon compound as the component (C) is used for improving the dispersibility of the organopolysiloxane as the component (A) and the hydrophobic fumed silica as the component (B). is there. The silicon compound may have a silicon atom number of 1 to 10 and a silanol group, but it is preferable that both terminals are silanol groups.
If the number of silicon atoms exceeds 10, the content of silanol groups will be small, and if it is added in a small amount, the dispersibility of silica will be poor, and if it is added in a large amount, the surface of the silicone rubber composition will become sticky, resulting in poor processability.

As the silicon compound, those represented by the following general formula (2) are particularly preferable.

[0022]

Embedded image (In the formula, R ² represents a methyl group, a phenyl group, a 3,3,3-trifluoropropyl group or a trimethylsiloxy group.)

Specific examples of such a silicon compound include the following.

[0024]

Embedded image

This silanol group-containing low-polymerization silicon compound is a diorganopolysiloxane 1 as component (A).
If it exceeds 3 parts by weight with respect to 00 parts by weight, the adhesion of the silicone rubber composition increases and the workability such as roll workability deteriorates, so 0 to 3 parts by weight, particularly 0.1 to 3 parts by weight is desirable.

In the present invention, the above (A) to
A silicone rubber composition can be obtained by uniformly mixing the component (C) using a rubber kneader such as a two-roll roll, a Banbury mixer, a dough mixer (kneader), and a heat treatment if necessary. . Normally, the silicone rubber composition is stored as U stock in this state,
Creep hardening occurs during storage and it becomes hard, and it is necessary to thoroughly knead it before vulcanization molding. This crepe hardening is observed faster due to accelerated heating. First, the Williams plasticity of a sufficiently kneaded silicone rubber composition was measured to be "initial plasticity", and 90
After the silicone rubber composition is allowed to cool for 30 minutes without kneading after 24 hours at ℃, the measured value of the Williams plasticity is referred to as "return plasticity", and the difference may be referred to as the Williams plasticity change. it can. In the silicone rubber composition according to the present invention, the change in Williams plasticity can be 50 or less.

The silicone rubber composition can be cured by either a conventionally known method utilizing a hydrosilylation reaction or a method in which an organic peroxide is used as a catalyst for vulcanization.

In the case of curing using a hydrosilylation reaction, an organohydrogenpolysiloxane and a platinum group metal-based catalyst as a curing agent can be added to the silicone rubber composition. In this case, the organopolysiloxane as the component (A) has two or more alkenyl groups in one molecule, preferably 0.00 in R ^1.
An alkenyl group is used in an amount of 1 to 5 mol%.

Here, the organohydrogenpolysiloxane may be any organopolysiloxane having two or more SiH groups in one molecule, and may be linear, cyclic or branched. However, those having a degree of polymerization of 300 or less are preferable. Further, such SiH group is
It may be at the end of the polysiloxane chain or at some midpoint. Such an organohydrogenpolysiloxane is
Alkenyl group 1 of the organopolysiloxane of component (A)
Usually 0.5 to 3 mol of SiH group, especially 1.0
Used in an amount ratio of ~ 2 mol. The platinum group metal-based catalyst used at the same time acts as a catalyst for the hydrosilylation reaction between the alkenyl group in the organopolysiloxane (A) and the SiH group in the organohydrogenpolysiloxane. It is usually used in the range of 0.1 to 1,000 ppm, preferably 1 to 100 ppm (as platinum metal) based on the total amount of the organopolysiloxane and the organohydrogenpolysiloxane. Examples of such platinum group metal-based catalysts include fine powder metal platinum catalysts described in US Pat. No. 2,970,150, chloroplatinic acid catalysts described in US Pat. No. 2,823,218, and US Pat. Patent No. 3,159,6
01 and 3,159,662, platinum-hydrocarbon complex compounds, U.S. Pat. No. 3,516,946.
Chloroplatinic acid-olefin complex compound,
U.S. Pat. Nos. 3,775,452 and 3,814,78
The platinum-vinyl siloxane complex described in No. 0 and the like can be used.

In the case of curing by hydrosilylation reaction, a reaction control agent such as methylvinylcyclotetrasiloxane and acetylene alcohols should be added in order to have good storage stability at room temperature and to maintain an appropriate pot life. You can also

On the other hand, when using an organic peroxide as a catalyst, the organic peroxide is added to the silicone rubber composition.
As the organic peroxide, benzoyl peroxide, bis (2,4-dichlorobenzoyl) peroxide, bis-orthochlorobenzoyl peroxide, 2,
5-dimethyl-bis (2,5-t-butylperoxy)
Hexane and the like can be used, and these may be used alone or in combination of two or more. The addition amount thereof is usually 0.01 to 3 parts by weight, preferably 0.05 to 1 part by weight, based on 100 parts by weight of the organopolysiloxane, and the composition can be extruded and heat-cured.

The silicone rubber composition of the present invention may be blended with a filler such as ground quartz, calcium carbonate or precipitated silica as an extender, if necessary. Also,
It is optional to add various additives such as a colorant and a heat resistance improver, a reaction control agent, a release agent or a dispersant for a filler, if necessary.

[0033]

EFFECTS OF THE INVENTION The silicone rubber composition of the present invention has low crepe hardening properties and exhibits little change in Williams plasticity even when stored for a long period of time before the addition of the vulcanizing agent.

[0034]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Example 1 Dimethylsiloxane unit 9
9.95 mol%, methyl vinyl siloxane unit 0.02
100 parts by weight of a gum-like organopolysiloxane having 5 mol% and 0.025 mol% of dimethylvinylsiloxane units, an average degree of polymerization of about 8,000, and a terminal unblocking rate of 8%, and octamethylcyclo Hydrophobic fumed silica surface-treated with tetrasiloxane (specific surface area 151
m ² / g, adsorbed carbon amount 2.1%, hydrophobicity 62%) 4
A silicone rubber composition was produced by mixing and dispersing 5 parts by weight and 0.5 parts by weight of 1,3-dihydroxytetramethyldisiloxane with a two-roll mill.

Example 2 Dimethylsiloxane unit 9
9.95 mol%, methyl vinyl siloxane unit 0.02
100 parts by weight of a gum-like organopolysiloxane having 5 mol% and 0.025 mol% of dimethylvinylsiloxane units, an average degree of polymerization of about 8,000, and an unblocked ratio of terminals of 8%, 1,3 -Hydrophobic fumed silica surface-treated with dihydroxytetramethyldisiloxane (specific surface area 130 m ² / g, adsorbed carbon amount 3.8%, hydrophobicity 7
0%) and 45 parts by weight of 1,3-dihydroxytetramethyldisiloxane were added and dispersed in a kneader and heat-treated at 180 ° C. for 2 hours to produce a silicone rubber composition. did.

Example 3 Dimethylsiloxane Unit 9
9.95 mol%, methyl vinyl siloxane unit 0.02
Dimethyldichlorosilane was added to 100 parts by weight of a gum-like organopolysiloxane having 5 mol% and dimethylvinylsiloxane unit of 0.025 mol%, an average degree of polymerization of about 8,000, and a terminal unblocking rate of 8%. 45 parts by weight of hydrophobic fumed silica surface-treated with (specific surface area 230 m ² / g, adsorbed carbon amount 2.2%, hydrophobicity 58%)
1,3-dihydroxytetramethyldisiloxane 1.
What added 0 weight part was mixed and disperse | distributed with the 2 roll, and the silicone rubber composition was manufactured.

Example 4 Dimethylsiloxane Unit 9
9.95 mol%, methyl vinyl siloxane unit 0.02
100 parts by weight of a gum-like organopolysiloxane having 5 mol% and 0.025 mol% of dimethylvinylsiloxane units, an average degree of polymerization of about 8,000, and a terminal unblocking rate of 8%, and octamethylcyclo Hydrophobic fumed silica surface-treated with tetrasiloxane (specific surface area 151
m ² / g, adsorbed carbon amount 2.1%, hydrophobicity 62%) 4
5 parts by weight, 0.3 parts by weight of 1,3-dihydroxy-1,3-dimethoxy-1,3-dimethyldisiloxane were mixed and dispersed with a kneader, and heat-treated at 150 ° C. for 1 hour, A silicone rubber composition was produced.

Example 5 Dimethylsiloxane Unit 9
9.95 mol%, methyl vinyl siloxane unit 0.02
100 parts by weight of a gum-like organopolysiloxane having 5 mol% and 0.025 mol% of dimethylvinylsiloxane units, an average degree of polymerization of about 8,000, and an unblocked rate of terminals of 8%, and dimethyldisilanol. 45 parts by weight of hydrophobic fumed silica (specific surface area 183 m ² / g, adsorbed carbon amount 2.5%, hydrophobicity 62%) surface-treated with
3-dihydroxy-1,3-ditrimethylsiloxy-
A silicone rubber composition was produced by mixing and dispersing 1,2-dimethyldisiloxane in an amount of 0.2 parts by weight with a two-roll mill.

Comparative Example 1 Dimethylsiloxane Unit 9
9.95 mol%, methyl vinyl siloxane unit 0.02
Hydrophilic fog was added to 100 parts by weight of a gum-like organopolysiloxane having 5 mol% and dimethylvinylsiloxane unit of 0.025 mol%, an average degree of polymerization of about 8,000, and a terminal unblocking rate of 8%. Quality silica (Reorosil Q
S102, manufactured by Tokuyama Co., Ltd.) and 45 parts by weight of silanol dimethylpolysiloxane at both ends (average polymerization degree of 10) were added and mixed and dispersed in a kneader, and heated at 180 ° C. for 2 hours to give a silicone rubber composition. Manufactured.

Comparative Example 2 Dimethylsiloxane Unit 9
9.95 mol%, methyl vinyl siloxane unit 0.02
100 parts by weight of a gum-like organopolysiloxane having 5 mol% and dimethylvinylsiloxane unit of 0.025 mol%, an average degree of polymerization of about 7,800, and a terminal unblocking rate of 8%, and hydrophobic fumes. Quality silica (specific surface area 125
m ² / g, adsorbed carbon amount 0.9%, hydrophobicity 47%) 4
A silicone rubber composition was produced by mixing and dispersing 5 parts by weight and 3 parts by weight of 1,3-dihydroxytetramethyldisiloxane in a two-roll mill.

Comparative Example 3 Dimethylsiloxane Unit 9
9.95 mol%, methyl vinyl siloxane unit 0.02
100 parts by weight of a gum-like organopolysiloxane having 5 mol% and 0.025 mol% of dimethylvinylsiloxane units, an average degree of polymerization of about 8,000, and a terminal unblocking rate of 8%, and hydrophobic fumes. Silica (specific surface area 217
m ² / g, adsorbed carbon amount 2.0%, hydrophobicity 44%) 4
What added 5 weight part was mixed and disperse | distributed with the 2 roll, and the silicone rubber composition was manufactured.

First, these compositions were sufficiently kneaded with a two-roll mill, and the initial Williams plasticity was measured. 9 more
After the lapse of 24 hours at 0 ° C., the composition was allowed to cool for 30 minutes without repeating, and the return Williams plasticity was measured.
The change in plasticity was calculated from the difference. In addition, 2,4-dichlorobenzoyl peroxide (50%
The product was added with 1.5 parts by weight, press-cured at 120 ° C. for 10 minutes, and post-cured at 200 ° C. for 4 hours, and the physical properties of rubber were measured. The results are shown in Table 1.

[0044]

[Table 1]

Example 6 and Comparative Example 4 A silicone rubber composition was prepared in the same manner as in Example 1 except that the gum-like organopolysiloxane having an average degree of polymerization of about 7,800 and an unblocked end ratio of 30% was used. An article was manufactured, and its characteristic value was measured in the same manner as above. Table 2 shows the results.

For comparison, in Example 1, 1, 3
A silicone rubber composition was prepared in the same manner except that 0.5 part by weight of dihydroxytetramethyldisiloxane was used instead of 8 parts by weight of silanoldimethylpolysiloxane having both terminals. Table 2 shows the characteristic values. In addition, the obtained composition had stickiness on the surface and had roll adhesion. Further, when 3 parts of silanol dimethyl polysiloxane having both terminals were used, the blending could not be successful.

[0047]

[Table 2]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takao Uno 1 Hitomi, Oita, Matsuida-cho, Usui-gun, Gunma 10 Shin-Etsu Chemical Co., Ltd. Silicone Electronic Materials Research Laboratory

Claims (4)

[Claims] 1. (A) The following average composition formula (1) R ¹ _n SiO _{(4-n) / 2} (1) (wherein, R ¹ is the same or different and is an unsubstituted or substituted monovalent hydrocarbon group. , N is a positive number from 1.98 to 2.02), and 100% by weight of the organopolysiloxane represented by the formula (B), the amount of adsorbed carbon is 2% by weight or more, and the hydrophobicity is 50% by volume or more. A silicone rubber composition comprising 10 to 70 parts by weight of fumed silica and 0 to 3 parts by weight of (C) a silanol group-containing low-polymerization silicon compound having 1 to 10 silicon atoms. 2. The composition according to claim 1, wherein the organopolysiloxane as the component (A) has a terminal unblocking ratio of 20 mol% or less. 3. A silanol group-containing low polymerization degree silicon compound as the component (C) has the following general formula (2): The composition according to claim 1 or 2, wherein R ² represents a methyl group, a phenyl group, a 3,3,3-trifluoropropyl group or a trimethylsiloxy group. 4. The composition according to claim 1, wherein the change in Williams plasticity is 50 or less.