JPS59204526A - Preparation of molded silicone rubber article - Google Patents

Abstract

PURPOSE:To make it possible to perform molding over a large number of times by using the same bath, by using diorganopolysiloxane having at least two alkenyl groups each directly bonded to a silicon atom in one molecule thereof. CONSTITUTION:Diorganopolysiloxane A having at least two alkenyl groups each directly bonded to a silicon atom in one molecule thereof, organohydrogenpolysiloxane B having at least two hydrogen atoms each directly bonded to a silicon atom in one molecule thereof, an inorg. filler C, a platinum type catalyst D and a curing reaction retarder E are uniformly mixed to prepare a liquid organopolysiloxane composition of which the viscosity is 10-1,000,000 centipoise at 25 deg.C and the pot life is 10 days or more at 25 deg.C. A mold held to a temp. range of 150-250 deg.C is immersed thus prepared composition for a predetermined time and, after drawing-up, demolding is performed to obtain a product. By using the same compositional bath, the above mentioned immersion molding can be repeated several times.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a silicone rubber molded article by a dip molding method using a liquid organopolysiloxane composition as a raw material.

As a manufacturing method of this kind, Japanese Patent Application Laid-Open No. 54-117556
No. 1, a method of forming a liquid organopolysiloxane composition by immersing a mold at a temperature in the range of 50 to 140 DEG C. is proposed. However, this manufacturing method has the disadvantage that the mold temperature is low, resulting in slow curing speed and low manufacturing efficiency.

It is necessary to use an organopolysiloxane composition with a short pot life, and the disadvantage is that the organopolysiloxane composition itself in the bath tends to thicken or harden, and the silicone rubber molded product cannot be molded multiple times using the same bath. The disadvantage is that it is difficult to do. Therefore, the present inventors have developed a method that has high production efficiency, stabilizes the organopolysiloxane composition in the bath, and allows silicone rubber molded products to be removed by multiple moldings using the same bath. As a result of research, the present invention was completed.

That is, the present invention provides (a) a diorganopolysiloxane having at least two alkenyl groups directly bonded to a silicon atom in one molecule;

(b) Organohydrodiene polysiloxane having at least two hydrogen atoms directly bonded to silicon atoms in one molecule.

(c) Inorganic filler.

(d) A platinum-based catalyst and (e) a curing reaction retarder, which has a viscosity at 925°C of 10 to 1,000,000.
The method is characterized by immersing a mold in a temperature range of 150 to 250°C in a liquid organopolysiloxane composition having 0 centivoise and a pot life of 10 days or more at 25°C, and removing the mold by pulling it up. The present invention relates to a method for manufacturing silicone rubber molded products.

The method of the present invention will be explained in detail below.

The diol 5-ganoborisiloxane used as the component (a) used in the present invention is a diol 5-ganoborisiloxane having a linear or branched structure, and has a wide range of properties ranging from oil-like to gum-like. range, especially 10 to 1,000,0
00 cm voice (25°C), preferably 500~
Various degrees of polymerization can be used, selected from those having a viscosity of 50,000 centipoise (25° C.). In the presence of the components (to be described later) and a platinum-based catalyst,
In order to undergo an addition reaction to form a silicone rubber, each molecule must have at least two alkenyl groups directly bonded to a silicon atom.

Examples of organic groups directly bonded to silicon atoms include alkyl groups such as methyl, ethyl, propyl, and butyl, aryl groups such as phenyl and tolyl, alkenyl groups such as vinyl and allyl groups, and carbonized groups thereof. Examples include groups in which part of the hydrogen atoms bonded to carbon atoms of the hydrogen group is substituted with a halogen atom, a cyano group, or the like.

The molecular chain end groups of this diol novolisiloxane are not particularly limited, but include triorganosilyl groups, for example,
Examples include a trimethylsilyl group, a diphenylmethylsilyl group, a dimethylvinylsilyl group, and a methylphenylvinylsilyl group, and among these, a group having a vinyl group is preferred.

This component may be used as a mixture of a low viscosity product and a high viscosity product.6 Firstly, the organohydrodiene polysiloxane as the component (b) must contain at least two molecules directly bonded to a silicon atom in one molecule. These hydrogen atoms are required to form a crosslinking bond through an addition reaction between the hydrogen atoms and the alkenyl group in (i) I&, and are blended in order to cure the composition. be. This (b) component is a linear organohydrogen whose molecular chain terminal is blocked with a triorganosilyl group and whose molecular chain is composed of only organosiloxane units or this and diorganosiloxane units. Empolysiloxane, linear diorganopolysiloxane in which both ends of the molecular chain are blocked with diorganohydrodienesilyl groups, and cyclic organohydrogenolysiloxane composed of only organohydrodienesiloxane units or this and diorganosiloxane units. Enpolysiloxane, organohydrodienepolysiloxane having a branched structure, and the like can all be used. The viscosity is 1 to 500 centiboise (2
5°C) is preferably used. Examples of the organic group directly bonded to a silicon atom include alkyl groups such as methyl and propyl groups, heptalyl groups such as phenyl and tolyl groups, and fluoroalkyl groups. Specific examples of these include the following.

However, in each formula, Me and Ph represent a methyl group and a phenyl group, respectively.

e: An integer of 2 or more f: 0 or a positive integer 1+: O or a positive integer i: 0 or a positive integer 8- j: An integer of 2 or more: 0 or a positive integer j+ = 3 to 8 (6 ) 8% co-hydrolyzed condensate represented by the average composition formula (% formula %) b, c: Each positive number (b) component contains two hydrogen atoms directly bonded to a silicon atom in one molecule as described above. (a) alkenyl groups directly bonded to silicon atoms in one molecule and (b) a total of five or more hydrogen atoms directly bonded to silicon atoms in one molecule of component are used. The following combination is appropriate.

The amount of component (b) is sufficient to provide 0.5 to 3.0 equivalents of hydrogen atoms directly bonded to the silicon atom per equivalent of the alkenyl group directly bonded to the silicon atom in (i) I & Min. It is preferable to set the amount to a certain amount. (b) If the blending amount of the component is less than this range, the crosslinking will be insufficient and it will be impossible to obtain a silicone rubber molded product with high elasticity. If the amount is larger than the above range, the curing reaction tends to be slow, and the excess H-8i bonds gradually undergo dehydrogenation reaction, resulting in a dark color in the molded product and ultimately decreasing the crosslink density. is too high, making it impossible to obtain a silicone rubber molded product with good elasticity. in particular,(
b) Components 1 to 2 with a viscosity of 1'& min to 5 parts by weight
0 parts by weight is preferred.

(c) The inorganic filler used as I& may be any of those conventionally used in the production of silicone rubber, and finely powdered silica such as fume silica and precipitated silica is most commonly used. There is.

Other slightly coarse particles include diatomaceous earth, silica fillers such as quartz fine powder, iron oxide, titanium oxide, aluminum oxide, calcium carbonate, clay, zinc white, aluminum silicate, calcium silicate, and carbon black. Inorganic fillers such as Among these, silica-based fillers are preferred, and mixtures of hume silica and quartz fine powder are more preferred.

The amount of component (c) to be blended is preferably 10-20 to 200 parts by weight per 100 parts by weight of component (a).

(d) The platinum-based catalyst for I& is required to promote the addition reaction between component (a) and component (b).
Examples of these include platinum black, chloroplatinic acid, complex salts of chloroplatinic acid and olefins, complex salts of platinum and vinyl siloxane, complex salts of chloroplatinic acid and vinyl siloxane, and chloroplatinic acid-alcohol coordination compounds. is used in a so-called catalytic amount, that is, approximately 1 to 500 ppm (weight ratio) of platinum, based on the total amount of components (a) and (b). The amount can be increased or decreased as appropriate depending on the reactivity of the components and the desired curing speed.

The curing reaction retarder of component (e) is an additive that delays the addition reaction and curing of component (a) and component (b) due to the catalytic action of component (d). These include benzotriazole, quinoline, picoline, nitrogen-containing compounds such as N,N'-dimethylformamide, trialkylphosphines,
Containing compounds such as trialkyl phosphates, 3-methyl-1-butyn-3-ol.

Examples include triple bond-containing compounds such as silanes represented by 3-methyl-1-penten-3-ol and 3,5-dimethyl-3-h, and methylvinyltetracyclosiloxane.

Only one type of this component may be added, or two or more types may be added. This component is the pot life at 25° C. of the organopolysiloxane composition consisting of (i) I#, min to (d) component.

That is, it is added so that the time for the viscosity to reach 1.5 times the initial viscosity (this is how pot life is defined in the present invention) is 10 days or more, preferably 30 days or more.

Specifically, as a rough guide, (a) component 100
Parts by weight, (B) component 1 to 20 parts by weight, (c) component 20 to
200 parts by weight.

(d) Add 0.01 to 1.5 parts by weight based on the amount of component catalyst.

In addition, pigments, heat resistance improvers, oil resistance improvers, fluidity improvers (e.g., dimethylpolysiloxane endblocked with trimethylsilyl groups at both ends, which is liquid at room temperature), reinforcing agents (e.g.,
CH3')3S i 0172 units, (CH*)2(O
A silicone resin consisting of H2=CH)SiO1/2 units and 5i04'72 units and containing 0.2 to 5% by weight of vinyl groups may be added to the extent that the object of the present invention is not impaired. Among these, dimethylpolysiloxanes which are liquid at room temperature and have a viscosity of 2 to 100 centivoise at 25°C and which are blocked at both ends with trimethylsilyl groups are used.
0 parts by weight, and ('CHa)3Sil/2 units, (
CH,)2 (CH2=CH) S i Consisting of O1/2 units and 5i04/2 units, Vinyl/L4 is 0.
10 to 100 parts by weight of silicone resin containing 2 to 5% by weight of (a) 100 parts by weight of 1&min; (b) components 1 to 20 parts by weight;
parts by weight, (jl) component 20 to 200 parts by weight, (d) component catalyst amount.

It is preferably added to 0.01 to 1.5 parts by weight of component (e).

In the method of the present invention, first, the above-mentioned (a) to (e)
Each of the components is uniformly mixed by a conventionally known mixing means until the viscosity at 25° C. is 10 to 1,000. It is OOO centiboise, and the pot life at 25℃ is 1.
The liquid organopolysiloxane composition is designed to last for 0 days or more, but usually for the purpose of long-term storage, it is divided into two packages and mixed together before use. It is advantageous to take The viscosity of the liquid organopolysiloxane composition in the present invention was measured using a BH type rotational viscometer, No. 60-ta.
0. This is the value after 1 minute at rpm.

It is particularly preferable that the liquid organocucle 150 xane composition obtained by mixing components (a) to (e) as described above has a viscosity of 500 to 50,000 centiboise. If the composition has a void size of 10 centimeter or less, the wall thickness of the silicone rubber molded product will be extremely thin. If the viscosity is higher than 1,013- o o, o o o centivoise, it will be difficult to obtain a silicone rubber molded product with uniform wall thickness. Such a viscosity is used (
This can be easily achieved by appropriately selecting the viscosity of the diorganopolysiloxane as the component (a), the type and amount of the inorganic filler as the component (c), etc. Further, the pot life at 25° C. is 10 days or more, preferably 30 days or more. If the pot life is less than 10 days, the number of continuous moldings will be significantly reduced.

In carrying out the method of the present invention, the dip molding itself may be performed according to a conventionally known method, but the heating temperature of the mold is 150 to 250 °C, preferably 155 to 21 °C.
The temperature is required to be in the range of 0°C, and if it is less than 150°C, the molded product will not be sufficiently cured and the post-heating operation will take a long time. On the other hand, if the temperature is higher than 2.50°C, air bubbles will form in the layers of the molded product, resulting in poor appearance.

The time for which the heated mold is immersed in the composition varies depending on the thickness of the intended molded product and the specific temperature of the mold, so it cannot be stated uniformly.
A rough guideline is 120 to 5 seconds at a mold temperature of 150 to 250°C. After being immersed for a predetermined period of time, it is taken out of the composition and, in general 14-, is further post-heated in a heating furnace. After heating, the product is obtained by molding and demolding.

Examples of the material of the mold include aluminum, brass, copper, iron, and stainless steel. The shape of the mold is not particularly limited. For example, there are cylindrical or conical convex molds, and molds for insulating sleeves for continuous terminals.

According to the method of the present invention, various silicone rubber molded products,
For example, electrical insulation members, cap seals, gasoline injector caps, and other daily necessities can be easily manufactured.

On the other hand, the method of the present invention can also be suitably applied to a method of masking electrical component terminals.

Next, examples of the present invention will be given. However, in the following description, "parts" simply indicate "parts by weight", and the viscosity is the value at 25°C.

Example 1 (a) 100 parts of dimethylpolysiloxane with a viscosity of 10,000 centivoids, in which both ends of the molecular chain are blocked with dimethylvinylsilyl groups (
(b) 7.0 parts of hydrogenpolysiloxane with a viscosity of 10 centimeters and consisting of 50 mol% of dimethylsiloxane units and 50 mol% of methylhydrogensiloxane units, with both ends capped with trimethylsilyl groups (c) Average particle size of 5 μm River quartz powder 50
Part (d) 2-ethylhexyl alcohol solution of chloroplatinic acid (platinum content 2% by weight) 0
．． 1 part (e) Benzotriazole
Dip molding as described below was performed using a composition consisting of 0.3 parts of each of the above components. Note that this composition has a viscosity of 6.0
It had a pot life of about 13 days at 25°C.

Dip molding 2. A cylindrical convex mold made of aluminum (diameter 50 mm x length 15 mm) heated to 160°C was placed in the above composition.
cm) was immersed at a depth of 100I11 for 50 seconds, pulled up, heated in a heating furnace at 300°C for 30 seconds, and then demolded to obtain a silicone rubber molded product. When the thickness of this molded product was measured, it was found to be uniform at 0.7 mm, and the surface was smooth.

Example 2 (a) 100 parts of dimethylpolysiloxane with a viscosity of 2,000 centivoids, with both ends of the molecular chain capped with dimethylvinylsilyl groups, and (b) 1 part of the same organohydrodiene polysiloxane used in Example 1.
0 parts (c) 100 parts of quartz powder with an average particle diameter of 5 μm and hume silica with a specific surface area of 130 m2/g that has been hydrophobized with hexamethyldisilazane 2
Part 5.

(d) Silane expressed by 0.005 parts of a complex salt of chloroplatinic acid and divinyltetramethyldisiloxane (platinum content: 34% by weight) 0.05 parts The dip molding described below was carried out using a composition consisting of the above components. went. This composition had a viscosity of 12,000 centipoise and a pot life of about 34 days at room temperature (25°C).

Dip molding: 10 molds used in Example 1 at 180°C
After heating to a depth of 6 cm, 201
After being immersed for 7 seconds, it was pulled up, heated in an oven at 300 DEG C. for 20 seconds, and then demolded to yield cylindrical silicone rubber molded products (20 pieces).

When the wall thickness of this molded product was measured, it was found to be uniform at 1.3 mm, and there were no pinholes.

The above dip molding process can be repeated for 7 hours/day for 5 days using the same composition bath.

Example 3 (a) 50 parts of dimethylpolysiloxane with a viscosity of 2,000 centivoids, in which both ends of the molecular chain are blocked with dimethylvinylsilyl groups, and 50 parts of dimethylpolysiloxane, with a viscosity of 10,000 centivoids, in which both ends of the molecular chain are blocked with dimethylvinylsilyl groups. Part (b) 6.0 parts of the same organohydrodiene polysiloxane used in Example 1 (c)
100 parts of quartz powder with an average particle size of 5μ and a specific surface area of 20
0 m2/g of 72-musilica hydrophobized with trimethylchlorosilane 25 parts (d) 0.007 part of the same platinum catalyst used in Example 2 0.05 part of silane represented by 18- and 0.4 part of benzotriazole (to) (CH,)3Si○1/2 unit, (CH2=CH
)(CH3)2Si○1/2 unit and 5i04/2 unit, vinyl group polysiloxane
16 parts (h) Dimethylpolysiloxane oil paste containing 20% by weight of carbon black
Dip molding as described below was performed using two parts of the composition consisting of each of the above items. This composition had a viscosity of 10,000 centivoids and a pot life of about 44 days at room temperature (25°C).

Dip molding: Brass truncated conical mold heated to 170°C (upper diameter 1.5 cm x lower diameter 0.4 cm)
After immersing 20 pieces (length 7 cm) in the above composition at a depth of 2 cTIl for 15 seconds, they were pulled up and placed in a heating furnace at 350°C.
After heating for 0 seconds and then demolding, a truncated conical black silicone rubber molded product was obtained. The thickness of this molded product was measured and was found to be uniform, 1 mm, and the surface was smooth. Flame retardancy was UL94 Vl. Using the same composition bath, the above dip molding was carried out for 7 hours/day.
I got rid of it by repeating it for 0 days.

Example 4 The composition prepared in Example 3 was subjected to dip molding as described below.

Dip molding: The mold used in Example 2 was heated to 200°C, immersed in the above composition to a depth of 6 cm for 10 seconds, then pulled out, heated in an oven at 300°C for 20 seconds, and then demolded. As a result, a cylindrical silicone rubber molded article was obtained.

When the wall thickness of this molded article was measured, it was found to be uniform in IT nm and the surface was smooth. Flame retardant is UL94
It was Vl.

Using the same composition bath, the above dip molding could be repeated for 7 hours/day for 7 days.

Example 5 In the composition of Example 2, methylvinyltetracyclopolysiloxane was used instead of silane as component (e).
The number of continuous dip molding days for 3 parts was 3 days.

Applicant: Toray Silicone Co., Ltd. −21= 172

Claims (1)

[Scope of Claims] 1(a) A diorganopolysiloxane having at least two alkenyl groups directly bonded to a silicon atom in one molecule. (b) Organohydrodiene polysiloxane having at least two hydrogen atoms directly bonded to silicon atoms in one molecule. (c) an inorganic filler, (d) a platinum-based catalyst, and (e) a curing reaction retardant, which has a viscosity at 925°C of 10 to 1. OOo, 00
0 centipoise and a pot life at 25°C of 10 days or more, immersing the mold in a temperature range of 150 to 250°C,
A method for manufacturing a silicone rubber molded product, characterized by pulling it up and demolding it. 2 Component (a) is a diorganopolysiloxane having a vinyl group directly bonded to a silicon atom only at both ends, and (
Component (b) is an organohydrodiene polysiloxane having at least 1 to at least 3 hydrogen atoms directly bonded to silicon atoms in one molecule, and component (c) is a silica-based filler. The manufacturing method according to item 1. 3. The diorganopolysiloxane of component (a) has a viscosity of 500 to 50,000 centipoise at 25°C,
The manufacturing method according to claim 2, wherein the organohydrodiene polysiloxane as component (b) has a viscosity of 1 to 500 centiboise at 25°C. 4 Component (a) is 100 parts by weight, component (b) is 1 to 20 parts by weight
Weight part. The manufacturing method according to claim 3, wherein the component (c) is 20 to 200 parts by weight, the component (d) is a catalyst amount, and the component (e) is 0.01 to 1.5 parts by weight. 5 The diorganopolysiloxane of component (a) is dimethylpolysiloxane with both ends capped with dimethylvinylsilyl groups, and the organohydrodiene polysiloxane of component (b) has triol capped with nosilyl groups at both ends. The silica-based filler of the component (c) is a mixture of 10 to 190 parts by weight of quartz fine powder and 10 to 40 parts by weight of humic silica, and the component (d) The platinum-based catalyst is a platinum/vinylsiloxacyl complex salt, and the curing reaction retarder (e) is benzotriazole, methylvinylcyclopolysiloxane, or a silane represented by the formula %). The manufacturing method according to scope item 4. 6 In addition to each component (a), (b), (c), (d), (e), (CH3), Si○1/2 unit, (CH3)2(O
10 to 100 parts by weight of a silicone resin consisting of H2=CH)SiO1/2 units and S;04/2 units and containing 0.2 to 5% by weight of vinyl groups and having a viscosity of 2 to 100 centivoise at 25° C.9 The manufacturing method according to claim 5, which contains 5 to 40 parts by weight of dimethylpolysilane whose both ends are blocked with trimethylsilyl groups. 7 (c) Component hume silica has a specific surface area of 100 to 3
00tn 2/g surface hydrophobized hume silica, and the curing retardant component (e) is a mixture of benzotriazole and a silane represented by the formula % Formula %) Claims +f5
The manufacturing method according to item 6. 8. The manufacturing method according to claim 1, wherein the immersion time of the mold is 120 to 5 seconds. 9. The manufacturing method according to claim 8, wherein the mold is immersed, heated for 120 to 3 seconds in a heating furnace at 100 to 350°C, and demolded.