JPH07113085B2 - Method for producing silicone rubber thread - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a silicone rubber thread.

[Prior Art] Conventionally, as a method for obtaining a silicone rubber thread, the components of the liquid silicone rubber composition are mixed at room temperature or higher to prepare a liquid silicone rubber composition,
A method is known in which the composition is put in a mold and cured at a temperature of 120 ° C. or higher, and the obtained cured product is cut into a thread shape by a machine tool.

[Problems to be Solved by the Invention] However, it is difficult to obtain a thin and uniform silicone rubber thread by these conventional methods, and the productivity is poor.

Therefore, the present inventors have completed the present invention as a result of examining a method for producing a silicone rubber yarn which does not have such a problem.

An object of the present invention is to provide a method for producing a silicone rubber yarn, which enables obtaining a thin and uniform silicone rubber yarn.

[Means for Solving Problems and Their Actions] The above-mentioned object is to apply a liquid silicone rubber composition at a flow rate of 0.01 m /
It is achieved by discharging into a liquid having a temperature of 25 ° C. or more and flowing for more than a second to be cured.

Explaining this, the liquid silicone rubber composition used in the present invention comprises (A) an organopolysiloxane having at least two lower alkenyl groups in one molecule, and (B) at least two silicon atoms in one molecule. Organopolysiloxane having bonded hydrogen atom (C) Platinum catalyst 0.1 to 1000 parts by weight of platinum metal per 1 million parts by weight of the total amount of components (A) to (B) [however, per molecule of component (A)] And the total number of hydrogen atoms per molecule of component (B) is at least 5].

Explaining this, the component (A) is the main component of the organopolysiloxane that gives the silicone rubber, and is the component that undergoes an addition reaction with the component (B) by the catalytic action of the component (C) and cures. The component (A) needs to have at least two lower alkenyl groups bonded to silicon atoms in one molecule, and if the number of the lower alkenyl groups is less than 2, a network structure will not be formed, resulting in good curing. I can't get anything.
Examples of such lower alkenyl group include vinyl group, allyl group,
A propenyl group is exemplified. The lower alkenyl group may be present anywhere in the molecule, but is preferably present at least at the terminal of the molecule. Further, the molecular structure of this component may be linear, branched-containing linear, cyclic or network, but is preferably linear with or without slight branching. . The molecular weight of this component is not particularly limited, and includes from low viscosity liquid to very high raw rubber, but is not particularly limited, but it is preferable that the viscosity at 25 ° C. is 100 centipoise or more for the cured product to become a rubber-like elastic body. . Examples of such an organopolysiloxane include methylvinylpolysiloxane, a copolymer of methylvinylsiloxane and dimethylsiloxane, dimethylpolysiloxane having both ends dimethylvinylsiloxy group blocked, and dimethylsiloxane-methylphenyl having both terminals dimethylvinylsiloxy group blocked. Siloxane copolymer, dimethylsiloxane-diphenylsiloxane-methylvinylsiloxane copolymer with both terminals dimethylvinylsiloxy group blocked, dimethylsiloxane-methylvinylsiloxane copolymer with both terminals trimethylsiloxy group blocked, trimethylsiloxy group blocked with both terminals Dimethyl siloxane-methylphenyl siloxane-methyl vinyl siloxane copolymer, methyl (3,3,3-trifluoropropyl) polysiloxane with both ends blocked with methyl vinyl siloxy groups Both ends blocked by dimethylvinylsiloxy groups dimethylsiloxane - methyl (3,3,3
Trifluoropropyl) siloxane copolymer, CH ₂ = CH (CH
_{3) 2} and SiO _1/2 units (CH ₃₎ polysiloxane consisting ₃ SiO _1/2 units and SiO _4/2 units is illustrated. In the present invention, the above organopolysiloxane may be used in combination.

The component (B) used in the present invention is a cross-linking agent for the component (A), and the silicon atom-bonded hydrogen atom in this component is converted to a lower alkenyl group in the component (A) by the catalytic action of the component (C). It cures by an addition reaction. This (B) component is 1
Having at least two silicon-bonded hydrogen atoms in the molecule is necessary for it to act as a crosslinker.

The total number of alkenyl groups in one molecule of component (A) and silicon-bonded hydrogen atoms in one molecule of component (B) is at least 5. If it is less than 5, a net-like structure is not substantially formed and a good molded product cannot be obtained, which is not preferable.

The molecular structure of this component is not particularly limited, and may be linear,
It may be linear, including branched, or cyclic. The molecular weight of this component is not particularly limited, but in order to improve the compatibility with the component (A), the viscosity at 25 ° C is preferably 1 to 50,000 centipoise.

The amount of this component added is such that the molar ratio of the total amount of silicon-bonded hydrogen atoms in this component to the total amount of all lower alkenyl groups in component (A) is (0.5: 1) to (20: 1). The amount is preferably such that, when the molar ratio is less than 0.5: 1, it is difficult to obtain good curability, and when it exceeds 20: 1, the hardness tends to increase when the cured product is heated. . still,
When organosiloxanes containing a large amount of alkenyl groups are separately added for the purpose of reinforcement, it is preferable to add this component containing silicon atom-bonded hydrogen atoms corresponding to the alkenyl groups.

Specific examples of this component include methyl hydrogen polysiloxane having trimethylsiloxy groups blocked at both ends, dimethylsiloxane-methylhydrogen polysiloxane copolymer having trimethylsiloxy groups blocked at both ends, and dimethylhydrogensiloxy group blocked at both ends. dimethylsiloxane - methylhydrogensiloxane copolymer, dimethylsiloxane - methylhydrogensiloxane cyclic copolymers, (CH _{3) 2} consisting of HSiO _1/2 units and SiO _2/4 unit copolymer, (CH _{3) 3} SiO _{1/2 units, (CH 3) 2 HSiO 1} /2 units and SiO ₄ /
_{An example} is a copolymer composed of ₂ units.

The component (C) is a catalyst for addition-reacting a silicon atom-bonded hydrogen atom and an alkenyl group, and specific examples thereof include chloroplatinic acid, a solution thereof dissolved in an alcohol or a ketone, and a solution thereof aged. , Complex compounds of chloroplatinic acid and olefins, complex compounds of chloroplatinic acid and alkenyl siloxanes, complex compounds of chloroplatinic acid and diketones, platinum black and platinum supported on a carrier.

This component is added in a total amount of (A) and (B) components of 10
The amount of platinum-based metal is set to 0.1 to 1000 parts by weight with respect to 0,000 parts by weight, because the crosslinking reaction does not proceed sufficiently at 0.1 parts by weight or less and it is uneconomical at 1000 parts by weight or more.
When normally used, the amount of platinum metal added is preferably about 1 to 100 parts by weight.

The liquid silicone rubber composition used in the present invention may be mixed with a filler in order to adjust the fluidity and improve the mechanical strength of the molded product. As such a filler,
Reinforcing fillers such as precipitated silica, fumed silica, pyrogenic silica, fumed titanium oxide, ground quartz, diatomaceous earth, asbestos, aluminosilicates, iron oxides, zinc oxides,
Non-reinforcing fillers such as calcium carbonate are exemplified, and they may be used as they are or surface-treated with an organic silicon compound such as hexamethyldisilazane, trimethylchlorosilane and polymethylsiloxane. Further, to the organopolysiloxane composition used in the present invention, as an additive for suppressing the curing reaction, an acetylene compound, hydrazines, triazoles, phosphines, mercaptans, etc. may be added in a trace amount or in a small amount, There is no problem as long as the object of the present invention is not impaired. In addition, a pigment, a heat-resistant agent, a flame retardant, a plasticizer, or an organopolysiloxane having one alkenyl group in one molecule for lowering the modulus may be added, if necessary.

In the present invention, the constituent components of the liquid silicone rubber composition are contained in a temperature range of -60 ° C to + 5 ° C, preferably -30 ° C.
It is preferable to prepare a liquid silicone rubber composition by mixing in the range of ˜0 ° C.

This is because when the temperature is lower than -60 ° C, the organopolysiloxane used in the present invention tends to be gelled and cannot be ejected, and when the temperature exceeds + 5 ° C, the curing reaction proceeds during mixing and ejection is difficult. In addition, the mechanical strength of the obtained cured product may be greatly reduced.

Then, the liquid silicone rubber composition thus obtained is discharged into a liquid flowing at a flow rate of 0.01 m / sec or more and having a temperature of 25 ° C. or more to be cured to form a silicone rubber thread. Here, if the flow velocity is less than 0.01 m / sec, a silicone rubber thread having a uniform shape may not be obtained, which is not preferable. Further, if the curing temperature is lower than 25 ° C., the curing rate of the liquid silicone rubber composition is reduced and the productivity is reduced, which is not preferable.

The liquid used in the present invention is not particularly limited as long as it is a liquid capable of heating and curing the liquid silicone rubber composition, but it is a liquid that inhibits the curing of the liquid silicone rubber composition or a good solvent for the liquid silicone rubber composition. Should be avoided.

Specific examples of the liquid used in the present invention include water, liquid paraffin, waxes, and liquid compounds used in various heating media, such as dimethyl silicone oil and phthalic acid esters. Water is preferable because it has a large heat capacity and is easy to handle.

In the present invention, the flow direction of the liquid is not particularly limited, but it is preferable that the liquid flows in a fixed direction.

Specific examples of such a flow behavior include a horizontal flow that flows in a horizontal direction, a swirl flow that swirls in a concentric circle toward the center, a spiral flow, and a drop flow that flows from a high place to a low place.

In the method of the present invention, for example, a cooling device is connected to a well-known kneading and molding machine for liquid silicone rubber, and the components of the liquid silicone rubber composition are mixed in the molding machine to prepare a liquid silicone rubber composition. It can be carried out by discharging the composition into a flowing liquid, which is set to a temperature of + 25 ° C. or higher in advance, and curing the composition to form a silicone rubber thread, which is taken out from the liquid.

By using the method for producing a silicone rubber thread of the present invention, it is possible to efficiently produce a thin silicone rubber thread which is a rubber elastic body.

EXAMPLES Next, the present invention will be described with reference to examples. Some parts in the examples are parts by weight, and the viscosity is a value at 25 ° C.

Example 1 100 parts of dimethylpolysiloxane having a viscosity of 12,000 centipoise (vinyl group content 0.12% by weight) having both ends of the molecular chain blocked with dimethylvinylsiloxy groups, 5 parts of hexamethyldisilazane, and 2.5 parts of ion-exchanged water were uniformly added. After mixing, add 30 parts of fumed silica with a specific surface area of 300 m ² / g and add 1 under reduced pressure.
The mixture was heated and mixed at 70 ° C. for 2 hours. After cooling, methyl hydrogen polysiloxane with a viscosity of 10 centipoise (SiH content 1% by weight) with both ends of the molecular chain blocked with trimethylsiloxy groups was added and mixed to form a mixture having a viscosity of 6000 poise at a shear rate of 10 sec-1. Obtained (mixture A).

Next, to 100 parts of the same dimethylpolysiloxane as above, 5 parts of the same hexamethyldisilazane as above, 2.5 parts of ion-exchanged water
After uniformly mixing the parts, 30 parts of fumed silica having a specific surface area of 300 m ² / g was added, and heated and mixed at 170 ° C. for 2 hours under reduced pressure. After cooling, 1.0 part of an isopropyl alcohol solution of chloroplatinic acid (platinum content: 3% by weight) was added and mixed to obtain a mixture similar to the above (mixture B).

The mixture A and the mixture B were fed into a static mixer previously cooled to -20 ° C by using a pressure pump, and the mixture A and the mixture B were mixed at a ratio of 1: 1 (weight ratio). On the other hand, water with a temperature of 70 ° C was filled in a water tank equipped with a stirring blade for generating a spiral flow and a winding device in the central portion, and a spiral flow was generated in the water tank. Here, the rotation speed of the stirring blade is 50
It was 0 revolutions / minute, and the flow rate of warm water was 10 cm / sec around the water tank. Next, the liquid silicone rubber composition obtained above was continuously discharged to the peripheral portion of the hot water tank through a nozzle having a diameter of 0.2 mm. The filamentous uncured material discharged from the nozzle flowed and hardened in warm water while drawing a circular orbit. 200 m of the obtained silicone rubber thread was taken out of the water tank, and its appearance and physical properties were examined. The results were as follows.

Prepare the aquarium appearance uniform fluff without external diameter 200 microns Specific gravity 1.12 breaking strength 132 kg / cm ² breaking elongation 800% EXAMPLE height of 2 left end is beveled so as to be higher than the height of the right end portion A silicone rubber yarn winding device was attached to the right end of the device. Then 5 from the left end
% Of surfactant [ethylene oxide adduct of trimethylnonanol, nonionic surfactant manufactured by Union Carbide Corporation, Taditol TMN-6] at a temperature of 85 ℃ is introduced and discharged from the right end. The hot water was set to flow horizontally in the water tank at a speed of 20 cm / sec. Then, Example 1
The liquid silicone rubber composition obtained in 1. was continuously discharged to the left end of the hot water tank through the same nozzle as in Example 1. The filamentous uncured material discharged from the nozzle flowed in warm water, was cured, and was then wound by a winding device. When the appearance and physical properties of the obtained silicone rubber yarn 200 m were examined, it was almost the same as that of the silicone rubber yarn obtained in Example 1.

EFFECTS OF THE INVENTION In the present invention, the liquid silicone rubber composition is discharged into a liquid flowing at a flow rate of 0.01 m / sec or more at a temperature of 25 ° C. or higher and cured to produce a silicone rubber thread, which is thin and uniform. It has a feature that a silicone rubber can be obtained.

Claims (2)

[Claims] 1. A liquid silicone rubber composition as described below, which has a flow rate of 0.
A method for producing a silicone rubber yarn, which comprises discharging into a liquid having a temperature of 25 ° C. or more and flowing at a rate of 01 m / sec or more to cure the silicone rubber thread. (A) Organopolysiloxane having at least two lower alkenyl groups in one molecule (B) Organopolysiloxane having at least two silicon-bonded hydrogen atoms in one molecule The molar ratio of the total amount to the total amount of all lower alkenyl groups in the component (A) is (0.5:
1) to (20: 1) (C) Platinum catalyst (A) to (B) The total amount of components is 1,000,000 parts by weight, and 0.1 to 1000 parts by weight of platinum metal [however, (A The total number of alkenyl groups per molecule of component (B) and the number of hydrogen atoms per molecule of component (B) is at least 5]. 2. The manufacturing method according to claim 1, wherein the liquid is water.