RUBBER PARTICLES, COMPOSITE PARTICLES AND PRODUCTION METHODS THEREOF

Abstract

Provided are polysiloxane structure-containing rubber particles and composite particles having a high dispersibility and degradability; and production methods thereof. The rubber particles are comprised of a copolymer having a polyester structure and an organopolysiloxane structure, wherein the copolymer is a hydrosilylation crosslinked product of (A) a polyester having at least two aliphatic unsaturated groups per molecule; and (B) an organohydrogenpolysiloxane having at least two silicon atom-bonded hydrogen atoms per molecule. The composite particles are those with the surfaces of these rubber particles being coated with polyorganosilsesquioxane or silica.

Claims

1. Rubber particles comprised of a copolymer having a polyester structure and an organopolysiloxane structure.

2. The rubber particles according to claim 1, wherein the rubber particles have a spherical shape and a volume average particle size of 0.1 to 50 μm.

3. The rubber particles according to claim 1, wherein the copolymer is a hydrosilylation crosslinked product of (A) a polyester having at least two aliphatic unsaturated groups per molecule; and (B) an organohydrogenpolysiloxane having at least two silicon atom-bonded hydrogen atoms per molecule, provided that excluded is a combination where there are two said aliphatic unsaturated groups per molecule of the component (A) and there are two said silicon atom-bonded hydrogen atoms per molecule of the component (B).

4. The rubber particles according to claim 3, wherein the component (A) which is the polyester having at least two aliphatic unsaturated groups per molecule is a component with molecular chain ends of a polyester or polyester copolymer having a linear or branched structure being substituted with aliphatic unsaturated groups.

5. The rubber particles according to claim 4, wherein the polyester structure of the component (A) is poly-ε-caprolactone.

6. The rubber particles according to claim 3, wherein the component (B) is an organohydrogenpolysiloxane having at least two silicon atom-bonded hydrogen atoms per molecule, which is represented by the following general formula (1): ##STR00012## wherein each R.sup.1 independently represents a substituted or unsubstituted monovalent hydrocarbon group having 1 to 30 carbon atoms; each R.sup.2 independently represents a hydrogen atom, or a substituted or unsubstituted monovalent hydrocarbon group having 1 to 30 carbon atoms; m satisfies 1≤m≤1,000; n satisfies 0≤n≤1,000; provided that when n=0, the two R.sup.2s are both hydrogen atoms, and that when neither of the two R.sup.2s is a hydrogen atom, n is 2 or larger.

7. The rubber particles according to claim 6, wherein the component (B) is an organohydrogenpolysiloxane having at least two silicon atom-bonded hydrogen atoms per molecule, which is represented by the following general formula (2): ##STR00013## wherein R.sup.3 represents a substituted or unsubstituted monovalent hydrocarbon group having 1 to 30 carbon atoms, other than a phenyl group; a, b and c satisfy 0≤a≤500, 1≤b≤1,000, 1≤a+b≤1,000, and 0≤c≤1,000; provided that when c=0, the two R.sup.2s are both hydrogen atoms, and that when neither of the two R.sup.2s is a hydrogen atom, c is 2 or larger.

8. Composite particles with the surfaces of the rubber particles according to claim 3 being coated with polyorganosilsesquioxane or silica.

9. A method for producing the rubber particles according to claim 3, comprising: (i) a step of obtaining an O/W type emulsion by adding, for emulsification, a surfactant- containing water phase component to an oil phase component comprised of (A) a polyester having at least two aliphatic unsaturated groups per molecule and (B) an organohydrogenpolysiloxane having at least two silicon atom-bonded hydrogen atoms per molecule; (ii) a step of obtaining (C) a rubber particle water dispersion by curing the oil phase component comprised of the components (A) and (B) in the emulsion via a hydrosilylation reaction under the presence of a hydrosilylation reactive catalyst; and (iii) a step of obtaining rubber particles by drying and removing water as a continuous phase from (C) the rubber particle water dispersion obtained in the step (ii).

10. A method for producing the composite particles according to claim 8, comprising: (i) a step of obtaining an O/W type emulsion by adding a surfactant-containing water phase component to an oil phase component and performing stirring, the oil phase component being comprised of (A) a polyester having at least two aliphatic unsaturated groups per molecule and (B) an organohydrogenpolysiloxane having at least two silicon atom-bonded hydrogen atoms per molecule; (ii) a step of obtaining (C) a rubber particle water dispersion by curing the oil phase component comprised of the components (A) and (B) in the emulsion via a hydrosilylation reaction under the presence of a hydrosilylation reactive catalyst; (iii′) a step of adding (E) an alkaline substance to (C) the rubber particle water dispersion obtained in the step (ii); (iv) a step of obtaining a composite particle water dispersion by adding (F) one kind selected from an organotrialkoxysilane or tetraalkoxysilane represented by the following general formula (3) and a hydrolysate thereof to the rubber particle water dispersion of the step (iii′) to which the alkaline substance has been added, whereby a condensation reaction is caused to allow the surfaces of the rubber particles to be coated with polyorganosilsesquioxane or silica, ##STR00014## wherein R.sup.4 represents a monovalent hydrocarbon group having 1 to 6 carbon atoms, R.sup.5 represents a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, or —OR.sup.4; and (v) a step of obtaining composite particles by drying and removing water as a continuous phase from the composite particle water dispersion obtained in the step (iv).

Description

WORKING EXAMPLES

[0132] The present invention is described in greater detail hereunder with reference to working and comparative examples; the invention shall not be limited to the following working examples. Further, in these examples, a dynamic viscosity is a value measured at 25° C.; “%” indicating concentrations and content rates refers to “% by mass”. A penetration degree of a rubber cured product is a value measured in accordance with the standards of the Society of Rubber Science and Technology, Japan (SRIS). The molecular weight of the component (A) is a weight-average molecular weight measured by GPC under the following conditions, with polystyrene being a reference substance.

Measurement Conditions

[0133] Developing solvent: Tetrahydrofuran (THF) [0134] Flow rate: 0.60 mL/min [0135] Detector: Differential refractive index detector (RI) [0136] Column: TSK Guardcolumn Super H-H [0137] TSK gel Super HM-N [0138] TSK gel Super H2500 [0139] (All manufactured by Tosoh Corporation) [0140] Column temperature: 40° C. [0141] Sample injection volume: 50 μL (THF solution with a concentration of 0.5% by mass)

Working Example 1

[0142] [Synthesis of Alkenyl Group-Containing poly-ε-caprolactone 1]

[0143] Here, 200 g of a poly(ε-caprolactone)diol (PLACCEL 205U by DAICEL CORPORATION, molecular weight 530, hydroxyl value 212.4 mg/g), 200 g of toluene and 95.8 g of triethylamine were added to a 1 L glass flask equipped with a stirrer, a dropping funnel, a thermometer and a cooling pipe, and mixed together at an adjusted temperature of 55° C., followed by using the dropping funnel to deliver thereinto by drops 168.9 g (an added amount at which there will be 1.1 chlorine atoms of an acid chloride per 1 hydroxyl group of the poly(ε-caprolactone)diol) of an undecenoic acid chloride, after which aging was performed for two hours. After aging, 200 g of water and 100 g of toluene were added, and the water phase was then moved to a separating funnel for extraction with 100 g of toluene. After extraction, the oil phase was washed with 450 g of water once and with 450 g of a saturated salt water twice, followed by adding 10 g of magnesium sulfate, 10 g of an activated carbon and 10 g of KYOWAAD 700 (by Kyowa Chemical Industry Co., Ltd.) to then perform shaking for two hours. After shaking, the magnesium sulfate, activated carbon and KYOWAAD 700 were eliminated via pressure filtration, and the solvent was distilled away at 60° C. and 10 mm Hg or lower, thereby obtaining an alkenyl group-containing poly-ε-caprolactone 1 (following formula (7)).

##STR00008##

(R.sup.6 represents an aliphatic group; 2≤m+n≤5; weight-average molecular weight: 862)

[0144] [Production of Rubber Particles]

[0145] Here, 171 g of the alkenyl group-containing poly-ε-caprolactone 1 synthesized and 83.46 g (an added amount at which there will be 1.1 hydrosilyl groups per 1 vinyl group) of a phenyl hydrogen polysiloxane represented by the following formula (8) and having a dynamic viscosity of 23 mm.sup.2/s, were put into a 1 L container, followed by using a homomixer to stir and dissolve them at 1,500 rpm. Next, as a result of adding 1.35 g of polyoxyethylene lauryl ether and 31.5 g of water, and then using a homomixer to perform stirring at 5,000 rpm, an O/W type emulsion was obtained and an increase in viscosity was observed, after which stirring was further continued for another 10 min. Next, while performing stirring at 1,500 rpm, 258.54 g of water was used to dilute the emulsion to obtain a white emulsion.

##STR00009##

[0146] This emulsion was then moved to a 1 L glass flask equipped with a stirrer employing anchor-shaped stirring blades, and had its temperature adjusted to 15 to 20° C., followed by delivering thereinto by drops, while performing stirring, a mixed solution of 1 g of an isododecane solution of a complex of platinum and vinyl group-containing disiloxane (platinum content 0.5%) and 0.68 g of polyoxyethylene lauryl ether, where stirring was performed for 30 min to 1 hour. Next, stirring was performed for two days with the temperature being adjusted to 40° C., thus obtaining a rubber particle water dispersion.

[0147] As a result of using an optical microscope to observe the shape of the rubber particles in the water dispersion obtained, it was confirmed that the rubber particles had a spherical shape; and as a result of measuring the volume average particle size thereof by an electrical resistivity method-particle size distribution measurement device (Multisizer 3 by Beckman Coulter Inc.), it was confirmed that the rubber particles had a volume average particle size of 5 μm.

[0148] After drying the water in the obtained rubber particle water dispersion with a spray dryer whose inlet temperature was set to 150° C. and whose outlet temperature was set to 80° C., there were obtained white to light yellow powdery rubber particles.

[0149] Further, the hardness of the rubber making up the rubber particles was measured as follows. The alkenyl group-containing poly-ε-caprolactone 1, the phenyl hydrogen polysiloxane represented by the formula (8), and the isododecane solution of the complex of platinum and vinyl group-containing disiloxane (platinum content 0.5%), were mixed at the above ratio and then poured into an aluminum petri dish so that the mixture would have a thickness of 10 mm therein. After leaving the same at 40° C. for two days, there was obtained a non-sticky (non-tacky) planar rubber. The hardness thereof was 63 as a result of conducting measurement using an Asker C durometer.

Working Example 2

[0150] [Production of Composite Particles]

[0151] A rubber particle water dispersion was obtained in a similar manner as the working example 1. Here, 357 g of the rubber particle water dispersion obtained was moved to a 2L glass flask equipped with a stirrer employing anchor-shaped stirring blades, where further added thereto were 602.5 g of water, 19 g of a 28% ammonia water solution and 1 g of a 40% dimethyldiallylammonium chloride polymer water solution (ME Polymer H40W by TOHO Chemical Industry Co.,Ltd.). The pH of the solution at that time was 11.3. After adjusting the temperature to 5 to 10° C., 25 min were spent in delivering thereinto by drops 20.5 g (an amount at which polymethylsilsesquioxane after the hydrolyzation and condensation reaction will be in an amount of 6.7 parts by mass per 100 parts by mass of the rubber particles) of methyltrimethoxysilane, during which the temperature of the solution was maintained at 5 to 10° C., and after which stirring was continued for another hour. Next, the solution was heated to 55 to 60° C. and stirred for an hour while maintaining such temperature, thereby completing the hydrolyzation and condensation reaction of methyltrimethoxysilane.

[0152] The solution prepared by hydrolyzing and condensing methyltrimethoxysilane in the rubber particle water dispersion was dehydrated to a water content of about 30%, using a pressure filtration device. The dehydration product was then moved to a 2 L glass flask equipped with a stirrer employing anchor-shaped stirring blades, followed by adding 1,000 g of water thereto to perform stirring for 30 min, after which dehydration was performed using the pressure filtration device. The dehydration product was again moved to the 2 L glass flask equipped with the stirrer employing the anchor-shaped stirring blades, followed by adding 1,000 g of water thereto to perform stirring for 30 min, after which dehydration was performed using the pressure filtration device. The dehydration product was dried at 105° C. in a hot air flow dryer, and the dried product was then crushed by a jet mill to obtain particles with fluidity.

[0153] As a result of observing the obtained particles with an electron microscope, it was confirmed that the particles were composite particles with the rubber particles being coated with a granular polyorganosilsesquioxane throughout the entire surfaces thereof (polyorganosilsesquioxane-coated rubber particles).

[0154] The composite particles obtained were then dispersed in water with a surfactant; and as a result of conducting measurement using the electrical resistivity method-particle size distribution measurement device (Multisizer 3 by Beckman Coulter Inc.), it was confirmed that the particle size distribution was at the same level as the above rubber particle water dispersion, and that the volume average particle size was 5 μm.

Working Example 3

[0155] A rubber particle water dispersion was obtained in a similar manner as the working example 1. Here, 265 g of the rubber particle water dispersion obtained was moved to a 2 L glass flask equipped with a stirrer employing anchor-shaped stirring blades, where further added thereto were 651.1 g of water, 2.2 g of a 2.8% ammonia water solution and 12 g (an amount at which lauryltrimethylammonium chloride will be in an amount of 0.44 parts per 100 parts by mass of water) of a 30% lauryltrimethylammonium chloride water solution (CATION BB by NOF CORPORATION). The pH at that time was 10.4. After adjusting the temperature to 5 to 10° C., 60 min were spent in delivering thereinto by drops 70.7 g (an amount at which silica after the hydrolyzation and condensation reaction will be in an amount of 27 parts by mass per 100 parts by mass of the rubber particles) of tetramethoxysilane, during which the temperature of the solution was maintained at 5 to 10° C., and after which stirring was performed for another three hours. Next, the solution was heated to 70 to 75° C. and stirred for an hour while maintaining such temperature, thereby completing the hydrolyzation and condensation reaction of tetramethoxysilane.

[0156] The composite particles obtained were then dispersed in water with a surfactant; and as a result of conducting measurement using the electrical resistivity method-particle size distribution measurement device (Multisizer 3 by Beckman Coulter Inc.), it was confirmed that the particle size distribution was at the same level as the above rubber particle water dispersion, and that the volume average particle size was 5 μm.

Working Example 4

[0157] [Synthesis of Alkenyl Group-Containing poly-ε-caprolactone 2]

[0158] Synthesis was conducted in a similar manner as the working example 1, except that 200 g of a poly(E-caprolactone)tetraol (PLACCEL 410 by DAICEL CORPORATION, molecular weight 1,030, hydroxyl value 216.7 mg/g) was used instead of 200 g of the poly(ε-caprolactone)diol (PLACCEL 205U by DAICEL CORPORATION), the amount of triethylamine was changed from 95.8 g to 98.4 g, and the amount of the undecenoic acid chloride was changed from 168.9 g to 173.5 g (an added amount at which there will be 1.1 acid chlorides per 1 hydroxyl group). As a result, an alkenyl group-containing poly-E-caprolactone 2 (weight-average molecular weight: 1,698) was obtained.

##STR00010##

(R.sup.9 represents an aliphatic group; 4≤k+l+m+n≤9; weight-average molecular weight: 1,698)

[0159] [Production of Rubber Particles]

[0160] A rubber particle water dispersion was obtained in a similar manner as the working example 1, except that 170 g of the alkenyl group-containing poly-ε-caprolactone 2 was used instead of 171 g of the alkenyl group-containing poly-ε-caprolactone 1, and that there were used 85.32 g (an added amount at which there will be 1.1 hydrosilyl groups per 1 vinyl group) of the phenyl hydrogen polysiloxane represented by the formula (8) and having the dynamic viscosity of 23 mm.sup.2/s. As a result of using an optical microscope to observe the shape of the rubber particles in the water dispersion obtained, it was confirmed that the rubber particles had a spherical shape; and as a result of measuring the volume average particle size thereof by the electrical resistivity method-particle size distribution measurement device (Multisizer 3 by Beckman Coulter Inc.), it was confirmed that the rubber particles had a volume average particle size of 5 μm. As is the case with the working example 1, after eliminating water with a spray dryer, there was obtained a white to light yellow powder. Further, as a result of measuring the hardness of the rubber making up the rubber particles in a similar manner as the working example 1, it was confirmed that the hardness of such rubber was 82.

Working Example 5

[0161] In a similar manner as the working example 2, polyorganosilsesquioxane-coated composite particles were obtained from the rubber particle water dispersion obtained in the working example 4. The composite particles obtained were then dispersed in water with a surfactant; and as a result of conducting measurement using the electrical resistivity method-particle size distribution measurement device (Multisizer 3 by Beckman Coulter Inc.), it was confirmed that the particle size distribution was at the same level as the above rubber particle water dispersion, and that the volume average particle size was 5 μm.

Working Example 6

[0162] Using the rubber particle water dispersion obtained in the working example 4, silica-coated composite particles were obtained in a similar manner as the working example 3. The composite particles obtained were then dispersed in water with a surfactant; and as a result of conducting measurement using the electrical resistivity method-particle size distribution measurement device (Multisizer 3 by Beckman Coulter Inc.), it was confirmed that the particle size distribution was at the same level as the above rubber particle water dispersion, and that the volume average particle size was 5 μm. As a result of observing these particles with an electron microscope, it was confirmed that the particles were composite particles with the surfaces of the rubber particles being coated with a granular silica.

Comparative Example 1

[0163] [Production of Planar Silicone Rubber]

[0164] Here, 25 g of a methylvinylpolysiloxane represented by the following formula (10) and having a dynamic viscosity of 600 mm.sup.2/s, and 1 g (an added amount at which there will be 1.1 hydrosilyl groups per 1 vinyl group) of a methyl hydrogen polysiloxane represented by the following formula (11) and having a dynamic viscosity of 27 mm.sup.2/s were put into a 100 mL container, and then stirred and dissolved. Next, 0.06 g of the isododecane solution of the complex of platinum and vinyl group-containing disiloxane (platinum content 0.5%) was added thereto to perform stirring, after which the mixture was poured into an aluminum petri dish so that it would have a thickness of 10 mm therein. After leaving the same at 40° C. for two days, there was obtained a planar rubber of a rubber composition of silicone particles. As a result of measuring the rubber hardness in a similar manner as the working example 1, it was confirmed that the hardness of this rubber was 60.

##STR00011##

[0165] [Evaluation on Hydrolyzability of Rubber (Measurement of Planar Rubber Hardness Over Time)]

[0166] Hydrolyzability was evaluated by the following method, with regard to the planar rubber (rubber hardness: 63) that was obtained in the working example 1 and was comprised of the alkenyl group-containing poly-ε-caprolactone 1 and the phenyl hydrogen polysiloxane represented by the formula (8); the planar rubber (rubber hardness: 82) that was obtained in the working example 4 and was comprised of the alkenyl group-containing poly-ε-caprolactone 2 and the phenyl hydrogen polysiloxane represented by the formula (8); and the planar rubber (rubber hardness: 60) that was obtained in the comparative example 1 and was comprised of the methylvinylpolysiloxane represented by the formula (10) and the methyl hydrogen polysiloxane represented by the formula (11).

[0167] The three kinds of planar rubber samples were placed and left to stand still in a thermo-hygrostat of a temperature of 70° C. and a humidity of 90% (model IW222 by Yamato Scientific Co., Ltd.), and changes in rubber hardness were measured on a day-to-day basis.

[0168] Further, the planar rubber (rubber hardness: 63) obtained in the working example 1 was left to stand still in a dryer of a temperature of 70° C. (model DNE601 by Yamato Scientific Co., Ltd.) as well as in an environment of room temperature and a humidity of up to 65% (simulating a usage environment), where changes in rubber hardness were measured on a day-to-day basis.

TABLE-US-00001 TABLE 1 Rubber hardness (AskerC) At the 15 days 30 days 45 days 60 days 75 days 95 days start later later later later later later Working example 1 63 58 35 Liquefied Liquefied Liquefied — Rubber sample Thermo-hygrostat Working example 4 82 82 82 73 56 25 Liquefied Rubber sample Thermo-hygrostat Comparative example 1 60 60 60 60 60 60 60 Rubber sample Thermo-hygrostat Working example 1 63 70 70 70 70 70 70 Rubber sample Dryer Working example 1 63 63 63 63 63 63 63 Rubber sample Room temperature, Humidity up to 65%

[0169] The planar rubber samples of the working examples 1 and 4 that were left to stand still in the thermo-hygrostat are assumed to have a degradability as they each had a structure where the alkenyl group-containing poly-ε-caprolactone and the organohydrogenpolysiloxane having the silicon atom-bonded hydrogen atoms were crosslinked under the presence of the hydrosilylation catalyst, and each exhibited a decrease in rubber hardness in the high-temperature and humidity environment of temperature 70° C., humidity 90%. In contrast, the planar rubber sample of the comparative example 1 is assumed to have no degradability as the ingredients thereof making up the rubber do not include one having a hydrolyzable functional group(s), such as polyester, and the rubber hardness thereof was constant even in the high-temperature and humidity environment. As for the planar rubber sample of the working example 1 that was left to stand still in the dryer of 70° C., while there was observed an increase in rubber hardness that was assumed to have been associated with a slight progression of hardening due to the heat, no decrease in rubber hardness was observed, from which it can be assumed that degradation would not occur unless under the presence of water. As for the planar rubber sample of the working example 1 that was left to stand still in the environment of room temperature and humidity up to 60%, simulating a usage environment, no decrease in rubber hardness was observed for a measurement period of 95 days, from which it can be assumed that the sample was stable in the actual usage environment for such measurement period.