KR20190035260A - Silicone rubber compositions - Google Patents

Abstract

The present invention relates to a silicone rubber composition having excellent antibacterial properties without degrading original properties of a silicone rubber. The silicone rubber composition of the present invention comprises organopolysiloxane, a filler, a processing aid, and an antibacterial agent, wherein the antibacterial agent includes silver (Ag) ions and zinc (Zn) ions.

Description

[0001] SILICONE RUBBER COMPOSITIONS [0002]

The present invention relates to a silicone rubber composition, and more particularly, to a silicone rubber composition having excellent antimicrobial activity.

Silicone rubber has excellent heat resistance, weather resistance and electrical insulation, and is used in various industrial fields. However, since such silicone rubber is also contaminated by fungi or bacteria, it may cause bacteria when applied to packings or medical products of food containers which require severe hygienic conditions. Therefore, in order to apply silicone rubber to food containers or medical products, antimicrobial properties should be imparted. To this end, an antimicrobial agent is generally added to the silicone rubber composition.

Korean Patent Laid-Open Publication No. 1998-0057368 discloses a silicone sealant composition having an antifungal effect by incorporating an organic antifungal agent such as benzimidazole, carbamate compound and isothiazolone compound into a silicone plasticizer solution. However, the above-mentioned organic antifungal agents such as benzimidazole, methylsulfonyl and the like are easily deteriorated due to changes in temperature, humidity, and light, so that the effect of preventing molds is difficult to be maintained.

Korean Patent Publication No. 2006-0032385 discloses a technique of using an antimicrobial agent having a silver (Ag) content of 80% or more as a method for compensating for the disadvantages of such an organic antifungal agent, and Korean Patent No. 289,625 discloses a method of using zeolite A technique of using an inorganic antibacterial agent as a carrier has been disclosed.

However, the simple addition of the above-mentioned inorganic antimicrobial agent to the silicone rubber still causes various problems such as discoloration of the silicone rubber, deterioration of the activity due to the high temperature treatment, increase in the amount of use, and inadequate food hygiene.

An object of the present invention is to provide a silicone rubber composition having excellent antimicrobial properties without deteriorating the inherent properties of the silicone rubber.

In order to achieve the above object, the present invention provides a silicone rubber composition comprising an organopolysiloxane, a filler, a processing aid, and an antimicrobial agent, wherein the antimicrobial agent contains silver (Ag) ion and zinc (Zn) Based on the total weight of the composition.

The silicone rubber composition of the present invention is excellent in antibacterial properties and can be used in various products requiring antibacterial properties, and has the advantage of maintaining the inherent properties of silicone rubber.

Hereinafter, the present invention will be described in detail.

The present invention provides a silicone rubber composition.

The silicone rubber compositions may include organopolysiloxanes, fillers, processing aids, and antimicrobial agents. Each component included in the silicone rubber composition of the present invention will be described in detail as follows.

Organopolysiloxane

The organopolysiloxane used as the main material in the silicone rubber composition according to the present invention has at least one functional group selected from the group consisting of aliphatic saturated hydrocarbon groups, aliphatic unsaturated hydrocarbon groups and aromatic unsaturated hydrocarbon groups at both terminals and side chains.

The organopolysiloxane is linear and comprises a repeating unit represented by the following formula (1).

[Chemical Formula 1]

R ¹ _a SiO _{(4-a) / 2}

Wherein R ¹ is an aliphatic saturated hydrocarbon group having 1 to 10 carbon atoms, an aliphatic unsaturated hydrocarbon group having 1 to 10 carbon atoms or an aromatic unsaturated hydrocarbon group having 6 to 10 carbon atoms, a is 1.5 to 2.5, specifically 1.90 To 2.05.

The aliphatic saturated hydrocarbon group may be an alkyl group having 1 to 10 carbon atoms, and more specifically may be a methyl group, an ethyl group, a propyl group, a hexyl group, an octyl group, a decyl group and the like. The aliphatic unsaturated hydrocarbon group may be an alkenyl group having 1 to 10 carbon atoms, more specifically, a vinyl group, a butenyl group, and the like. The aromatic unsaturated hydrocarbon group may be an aryl group having 6 to 10 carbon atoms, more specifically, a phenyl group, a methylphenyl group, an ethylphenyl group, or the like. The organopolysiloxane may specifically be represented by the following formula (2).

(2)

In the above formula (2), m + n is 3,000 to 10,000, and n is 0.01 to 10 mol% of the total m + n units. The organopolysiloxane may have a weight average molecular weight of 200,000 to 800,000, specifically 250,000 to 750,000, more specifically 300,000 to 700,000. When the weight average molecular weight of the organopolysiloxane is out of the above range, the crosslinking density of the silicone rubber composition becomes poor and the hardness after curing becomes excessively low or high.

In addition, the organopolysiloxane may have a viscosity of 5,000,000 cp or more at 25 ° C. When the viscosity of the organopolysiloxane is less than 5,000,000 cp, there is a problem that workability in coloring processing becomes poor.

In order to improve the mechanical properties and processability as described above, the organopolysiloxane may be a linear organopolysiloxane highly polymerized with 3,000 to 10,000 siloxane units.

Filler

In the silicone rubber composition according to the present invention, the filler may be a finely powdered synthetic silica such as a dry process silica or a wet process silica as a reinforcing filler, or a surface of the fine synthetic silica such as an organochlorosilane, an organoalkoxysilane, a hexaorganodisilazane, Fine-powder type synthetic silica treated with an oligomer or the like is used.

The fine powdery synthetic silica has a specific surface area of from 50 m ² / g to 500 m ² / g, more specifically from 70 m ² / g to 400 m ² / g, more specifically from 100 m ² / 300 m < ² > / g. When the specific surface area of the filler is out of the above range, the desired appearance and mechanical properties may not be exhibited.

The filler may be included in an amount of 5 to 200 parts by weight, specifically 7 to 150 parts by weight, more specifically 10 to 100 parts by weight, based on 100 parts by weight of the organopolysiloxane. When the content of the filler is less than 5 parts by weight, it is difficult to expect enhancement of mechanical properties. When the content of the filler exceeds 200 parts by weight, dispersion of the filler becomes difficult, and overall mechanical properties may be deteriorated due to high modulus.

Processing aid

In the silicone rubber composition according to the present invention, the processing aid may be included to maintain uniform mechanical properties by increasing the dispersing power of the filler, to suppress the occurrence of rough creep hardening and to increase the storage period.

The processing aid may include a compound represented by the following general formula (3) or a compound represented by the following general formula (5). In particular, in order to improve the mechanical properties of the silicone rubber composition, Compounds can be used together.

(3)

R ² - (R ⁴ R ⁵ SiO) _b -R ³

In the above formula (3), R ² and R ³ may each independently be a hydroxyl group or an alkoxy group having 1 to 10 carbon atoms, specifically, a hydroxyl group or an alkoxy group having 1 to 6 carbon atoms, A hydroxyl group or an alkoxy group having 1 to 3 carbon atoms, and particularly, R ² and R ³ may all be a hydroxy group. In Formula 3, R ⁴ and R ⁵ may each independently be an alkyl group having 1 to 10 carbon atoms, specifically, an alkyl group having 1 to 6 carbon atoms. In Formula 3, b is an integer of 1 to 100. In particular, the compound represented by Formula 3 may be a compound represented by Formula 4 below.

[Chemical Formula 4]

In Formula 4, x is an integer of 1 to 50.

[Chemical Formula 5]

R ⁶ - (R ⁸ R ⁹ SiO) _c - (R ¹⁰ R ¹¹ SiO) _d -R ⁷

In formula (5), R ⁶ and R ⁷ each independently represent a hydroxyl group or an alkoxy group having 1 to 10 carbon atoms, specifically, a hydroxyl group or an alkoxy group having 1 to 6 carbon atoms, A hydroxyl group or an alkoxy group having 1 to 3 carbon atoms, and particularly, R ⁶ and R ⁷ may all be a hydroxy group. In Formula 5, R ⁸ and R ⁹ each independently represent an alkyl group having 1 to 10 carbon atoms, specifically, an alkyl group having 1 to 6 carbon atoms. In formula (5), R ¹⁰ and R ¹¹ each independently represent an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 1 to 10 carbon atoms, specifically an alkyl group having 1 to 6 carbon atoms or an alkenyl group having 1 to 6 carbon atoms , And at least one of R ¹⁰ and R ¹¹ is an alkenyl group. In Formula 5, c and d are each independently an integer of 1 to 100. In particular, the compound represented by Formula 5 may be a compound represented by Formula 6 below.

[Chemical Formula 6]

In Formula 6, y and z are each independently an integer of 1 to 50.

The compound represented by Formula 3 and the compound represented by Formula 5 may independently have a viscosity of 100 cp or less at 25 ° C. If the viscosity exceeds 100 cp, there is a possibility that the adjustment of the strength (tearing) of the silicone rubber composition may not be easy.

The compound represented by Formula 3 and the compound represented by Formula 5 are each independently added in an amount of 0.01 to 30 parts by weight, specifically 0.5 to 20 parts by weight, per 100 parts by weight of the organopolysiloxane, more specifically, May be contained in an amount of 0.1 part by weight to 10 parts by weight. If the content of the compound represented by the general formula (3) and the content of the compound represented by the general formula (5) is less than 0.01 part by weight, dispersion of silica as a filler is difficult, while if it exceeds 30 parts by weight, there is a fear that workability is deteriorated due to stickiness of the composition have.

Antimicrobial agent

In the silicone rubber composition according to the present invention, the antibacterial agent may be included to impart the antibacterial property of the silicone rubber composition.

Wherein the antimicrobial agent contains 0.1 to 5% by weight of silver (Ag) ions and 10 to 15% by weight of zinc (Zn) ions and the silver ion and zinc ion are mixed with synthetic zeolite, hydroxyapatite, calcium phosphate, colloidal silica, Silica, alumina and glass. Specifically, the antimicrobial agent is a glass antimicrobial agent in which silver ions and zinc ions are supported on glass. In addition to the silver ions and zinc ions, oxygen (O), sodium (Na), magnesium (Mg), aluminum (Al), silicon (Si), phosphorus (P) and calcium (Ca)

If the content of the silver ion and the zinc ion is out of the above range, the antimicrobial properties may be insufficient or the physical properties of the final molded product may be deteriorated.

At this time, the silver ion and the zinc ion may be contained in a weight ratio of 1: 2 to 7, specifically 1: 4 to 7. If the mixing ratio is out of the above range, antibacterial properties may be deteriorated or yellowing may occur.

The antimicrobial agent may be contained in an amount of 0.01 to 30 parts by weight, specifically 0.5 to 20 parts by weight, more specifically 0.1 to 10 parts by weight, based on 100 parts by weight of the organopolysiloxane. When the content of the antimicrobial agent is less than 0.01 part by weight, the antimicrobial activity of a molded article made of a silicone rubber composition may be deteriorated. When the content of the antimicrobial agent exceeds 30 parts by weight, mechanical or chemical properties of the molded article may deteriorate or discoloration may occur in the molded article have.

In addition, the particle size of the antibacterial agent may be 1 to 40 탆. If the particle size of the antimicrobial agent is out of the above range, dispersion becomes difficult and coloring may occur in the molded article.

Release agent

In the silicone rubber composition according to the present invention, the release agent may be a metal salt of an organic fatty acid such as calcium stearate, magnesium stearate and zinc stearate, in particular a magnesium salt, a calcium salt or a zinc salt of an organic fatty acid.

The release agent may be included in an amount of 0.001 to 2 parts by weight, specifically 0.01 to 1 part by weight based on 100 parts by weight of the organopolysiloxane. If the content of the releasing agent is less than 0.001 parts by weight, there is no mold releasing effect. If the amount is more than 2 parts by weight, discoloration due to yellowing may occur on the appearance of the molded article.

Hardener

In the silicone rubber composition according to the present invention, the curing agent may be an organic oxide or a metal complex compound containing a curing retarder. The organic peroxide is capable of generating radicals by pyrolysis so that a radical reaction may proceed to a vinyl group of the organopolysiloxane to form a crosslink, and the alkyl peroxide may be an alkyl or an acyl group. The metal complex may be a platinum complex, and the curing agent may be 1-ethynyl-1-cyclohexanol, 1,1,3,3-tetramethyl-1,3-divinyldisilazane, Methyl-3-butyne-2-ol, and / or phosphite-based compounds (for example, Tris (2,4-di -tert-butylphenyl) phosphite).

For example, the organic peroxide may be 2,5-dimethyl-2,5-t-butylhexane peroxide (45% paste purity, mixed with silica and oil), 2,4-dichlorobenzoyl peroxide (50% Paste purity, mixed state with silica and oil), benzoyl peroxide (mixed with silica and oil in 50% paste purity), etc. These may be used alone or in combination of two or more kinds.

The curing agent may be contained in an amount of 0.01 to 12 parts by weight, specifically 0.1 to 10 parts by weight based on 100 parts by weight of the organopolysiloxane. If the content of the curing agent is less than 0.01 parts by weight, the silicone rubber may not be sufficiently cured. If the content of the curing agent is more than 12 parts by weight, the mechanical properties may be deteriorated and the post curing operation .

The silicone rubber composition of the present invention may contain, in addition to the above-mentioned components, additional conventional additives as needed, so long as the object of the present invention is not impaired.

Hereinafter, the present invention will be described in detail with reference to examples.

However, the following examples illustrate the present invention in detail, and the present invention is not limited by the following examples.

[ Example  1 to 5 and Comparative Example  1 to 10]

The organopolysiloxane, the processing aid, the releasing agent, the antibacterial agent, the filler and the curing agent were put into a kneader (Hermann Linden, LK Ⅲ 2) and uniformly dispersed at a temperature of 80 캜 according to the compositions shown in the following Tables 1 and 2, And then cooled and kneaded at 80 DEG C or lower for 1 hour to prepare a silicone rubber composition.

division Example 1 Example 2 Example 3 Example 4 Example 5 Organopolysiloxane 66.55 66.48 66.42 66.48 66.48 The first processing aid 2.18 2.18 2.18 2.18 2.18 The second processing aid 0.21 0.21 0.21 0.21 0.21 Release agent 0.02 0.02 0.02 0.02 0.02 First antimicrobial agent
(Silver ion: zinc ion (weight ratio)) 0.10
(1: 4.12) 0.20
(1: 4.34) 0.30
(1: 6.90) 0.20
(1: 2.22) 0.20
(1: 2.01) The silver ion content (wt%) in the first antimicrobial agent 2.5 2.9 2.1 7.4 8.8 The zinc ion content (wt%) in the first antimicrobial agent 10.3 12.6 14.5 16.4 17.7 Filler 30.43 30.40 30.36 30.40 30.40 Hardener 0.51 0.51 0.51 0.51 0.51

division Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Comparative Example 9 Comparative Example 10 Organopolysiloxane 66.55 66.55 63.38 66.48 66.48 66.48 66.48 66.48 66.48 66.48 The first processing aid 2.18 2.18 2.18 2.18 2.18 2.18 2.18 2.18 2.18 2.18 The second processing aid 0.21 0.21 0.21 0.21 0.21 2.21 2.21 2.21 2.21 2.21 Release agent 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 First antimicrobial agent
(Silver ion: zinc ion (weight ratio)) - - - 0.20
(1: 7.77) 0.20
(1: 7.95) 0.20
(1: 0.78) 0.20
(1: 1.66) 0.20
(1: 1.91) 0.20
(1: 18.75) 0.20
(1: 1.74) The silver ion content (wt%) in the first antimicrobial agent - - - 2.6 2.1 11.4 11.4 7.4 0.08 8.8 The zinc ion content (wt%) in the first antimicrobial agent - - - 20.2 16.7 8.9 18.9 14.1 1.5 15.3 Second antimicrobial agent 0.10 - - - - - - - - - The third antibacterial agent - 0.10 - - - - - - - - Fourth antimicrobial agent - - 4.86 - - - - - - - Filler 30.43 30.43 28.87 30.40 30.40 30.40 30.40 30.40 30.40 30.40 Hardener 0.51 0.51 0.48 0.51 0.51 0.51 0.51 0.51 0.51 0.51

- Organopolysiloxane: methyl vinyl silicone GUM (Siloxanes and Silicones, di-Me, Me vinyl, vinyl group-terminated (Cas No. 68083-18-1)

- First processing aid: Siloxanes and Silicones, di-Me, hydroxy-terminated (Cas No. 70131-67-8)

- Second processing aid: Siloxanes and Silicones, di-Me, Me vinyl, hydroxy-terminated (Cas No. 67923-19-7)

- Release agent: calcium threate

- First antimicrobial agent: glass antimicrobial agent containing silver ion and zinc ion (particle size: 12 탆)

- Second antibacterial agent: 3-Iodo-2-propynylbutylcarbamate

- Third antimicrobial agent: Dichloro-2-n-octyl-4-isothiazolin-3-one

- 4th Antimicrobial agent: A herb medicine ingredient (product name: ECOLEI, product of the company) containing 40 antifungal compounds such as flavonoid and polyphenol,

- Filler: wet silica (specific surface area 190 m ² / g)

- Hardener: 2,5-dimethyl-2,5-t-butylhexane peroxide (45% paste purity, mixed with silica and oil)

[ Experimental Example ]

The specimens made from the silicone rubber compositions of the Examples and Comparative Examples thus prepared were measured for mechanical properties as described below, and the results are shown in Tables 3 to 5 below.

(1) Hardness

Specimens were prepared and measured according to ASTM D2240.

Specifically, the hardness indicates the degree of hardness of the silicone rubber, and in the case of a general thermosetting silicone rubber, it ranges from a low hardness of at least 15 to 20 degrees to a hardness of up to 90 degrees. The measuring instrument shall be a SHORE A TYPE durometer. The thickness of the specimen shall be measured by overlapping 6 mm thick specimens or 3 specimens of 2 mm thickness and measuring within 1/2 inch from the edge. Within 1 second after the specimen is in contact with the specimen And repeatedly measured 5 times or more, and the average value is displayed as the hardness value.

(2)

If the degree of plasticity is low when working on a two-roll mill, it is difficult to pull out the sheet. When injected into an injection machine, It must be injected, but it breaks well and it hinders injector injecting work. The measuring instrument was plasticized (softened) for 5 minutes using a Williams Plasticity measurement method of JISK6249 and then subjected to a defoaming process for 2 minutes. Then, a mass of twice the specific gravity was sampled, and after cooling for 5 minutes The figure shows the degree of spread over 5 minutes under a load of 5 kg.

(3) Tear strength

The force acting per unit length is measured by quantifying how long the rubber will withstand when it is torn a little due to minor scratches or impacts in the environment of use. The measuring instrument uses a universal testing machine and the average value of four specimens is measured by pulling a silicone rubber specimen of ASTM D624-DIE C (DUMBBLE TYPE) specification at a speed of 500 mm / min.

(4) Tensile strength

The strength of the maximum stress per unit area of the silicone rubber specimen is expressed as a numerical value and expressed as tensile strength in terms of MPa and pound. The measuring machine uses a universal testing machine and the average value of the four specimens is measured by pulling the silicone rubber specimen of ASTM D412 specification at 500 mm / min.

(5) Elongation

The increase in length of the final specimen at the time of specimen fracture is expressed as a percentage of the original length of the specimen. The measuring instrument can be measured together with the universal testing machine when measuring the tensile strength.

(6) Antibacterial activity

 It was measured according to JIS Z 2801: 2010.

It is the most suitable method for analyzing the antimicrobial activity of plastics products using inorganic antibacterial agent, which is the migration of metal particles confined to the plastic surface. Inoculation of the microorganisms cultured on the surface of the sample, . The numerical value when the antibacterial activity is effective by this method is 99% or more (log value = active value 2).

division unit Example 1 Example 2 Example 3 Example 4 Example 5 Plasticity - 220 220 222 220 221 Hardness Shorea 63 63 64 63 63 The tensile strength Mpa 7.0 7.0 6.8 7.1 7.3 Elongation % 225 225 220 220 210 Tear _C N / mm 18.5 18.5 17.4 17.5 18.5 importance - 1.16 1.16 1.17 1.16 1.16 Exterior - Transparency Transparency Transparency Transparency Transparency Antimicrobial activity
(Staphylococcus aureus ATCC 658P) Log 2.2 2.4 2.2 2.1 2.2 Antimicrobial activity
(Escherichia coli ATCC 8739) 2.4 2.6 2.4 2.1 2.2

division unit Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Plasticity - 221 220 220 220 225 Hardness Shorea 62 62 63 63 62 The tensile strength Mpa 7.8 7.9 7.9 7.1 7.5 Elongation % 244 240 220 220 230 Tear _C N / mm 19.0 18.8 20.5 17.5 17.4 importance - 1.16 1.16 1.20 1.16 1.16 Exterior - Yellowing severity Yellowing opacity Transparency Transparency Antimicrobial activity
(Staphylococcus aureus ATCC 658P) Log 1.8 1.9 2.0 1.7 1.9 Antimicrobial activity
(Escherichia coli ATCC 8739) 1.9 1.9 2.0 1.8 1.8

division unit Comparative Example 6 Comparative Example 7 Comparative Example 8 Comparative Example 9 Comparative Example 10 Plasticity - 220 230 222 220 223 Hardness Shorea 62 62 61 62 61 The tensile strength Mpa 7.0 6.5 6.8 7.0 6.7 Elongation % 215 210 220 215 210 Tear _C N / mm 17.3 17 16.5 18 17.2 importance - 1.16 1.16 1.16 1.16 1.16 Exterior - Yellowing Yellowing Transparency Transparency Transparency Antimicrobial activity
(Staphylococcus aureus ATCC 658P) Log 2.4 2.5 1.8 1.5 1.7 Antimicrobial activity
(Escherichia coli ATCC 8739) 2.5 2.6 1.8 1.5 1.7

As can be seen from the results of Tables 3 to 5, all of the examples and comparative examples showed almost no difference in mechanical properties, but in the case of Examples 1 to 5, inorganic antibacterial agents containing both silver ions and zinc ions were applied The antimicrobial activity of the antimicrobial activity is 2.0 or more and the antimicrobial property is excellent. Also, the appearance is transparent without yellowing, and there is no color change even after coloring. However, in the case of Comparative Examples 1 and 2, it was found that the application of the organic antimicrobial agent resulted in yellowing and the antibacterial activity was lower than that of the inorganic antibacterial agent. In the case of Comparative Example 3, the application of the herbal medicine as an antimicrobial agent has good mechanical and antibacterial properties, but its appearance is unclear, making it difficult to apply it to a silicone rubber (product). On the other hand, in the case of Comparative Examples 4 to 10, inorganic antibacterial agents containing both silver ions and zinc ions were applied, but it was found that the antimicrobial properties were poor and yellowing occurred, Is out of the range of 1: 2 to 7, it is found that such a problem occurs.

Claims (5)

A silicone rubber composition comprising an organopolysiloxane, a filler, a processing aid, and an antimicrobial agent,
Wherein the antimicrobial agent comprises silver (Ag) ions and zinc (Zn) ions in a weight ratio of 1: 2 to 7. The method according to claim 1,
Wherein the antimicrobial agent comprises 0.1 to 5% by weight of silver ions and 10 to 15% by weight of zinc ions. The method according to claim 1,
Wherein the organopolysiloxane comprises a repeating unit represented by the following formula (1).
[Chemical Formula 1]
R ¹ _a SiO _{(4-a) / 2}
(Wherein R ¹ is an aliphatic saturated hydrocarbon group having 1 to 10 carbon atoms, an aliphatic unsaturated hydrocarbon group having 1 to 10 carbon atoms, or an aromatic unsaturated hydrocarbon group having 6 to 30 carbon atoms, and a is 1.5 to 2.5). The method according to claim 1,
Wherein the organopolysiloxane comprises a compound represented by the following formula (2).
(2)

(M + n in the above formula (2) is 3,000 to 10,000, and n is 0.01 to 10 mol% of the total m + n units.) The method according to claim 1,
Wherein the processing aid comprises a compound represented by the following formula (3) or a compound represented by the following formula (5).
(3)
R ² - (R ⁴ R ⁵ SiO) _b -R ³
(Wherein R ² and R ³ are each independently a hydroxyl group or an alkoxy group having 1 to 10 carbon atoms, R ⁴ and R ⁵ are each independently an alkyl group having 1 to 10 carbon atoms, and b is 1 ≪ / RTI >
[Chemical Formula 5]
R ⁶ - (R ⁸ R ⁹ SiO) _c - (R ¹⁰ R ¹¹ SiO) _d -R ⁷
(Wherein R ⁶ and R ⁷ are each independently a hydroxyl group or an alkoxy group having 1 to 10 carbon atoms, R ⁸ and R ⁹ are each independently an alkyl group having 1 to 10 carbon atoms, and R ¹⁰ and / R ¹¹ is independently an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 1 to 10 carbon atoms, at least one of R ¹⁰ and R ¹¹ is an alkenyl group, and each of c and d is independently an integer of 1 to 100 .)