JPS62240362A - Curable liquid polyorgnaosiloxane composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a liquid polyorganosiloxane composition that is cured by a hydrosilation reaction to produce an elastomer that is flexible, tough, and optically transparent. relating to things.

[Conventional technology]

It is known to prepare liquid or pumpable compositions by mixing together vinyl-containing polydiorganosiloxanes, organohydrogensiloxane curing agents, platinum-containing catalysts, and optionally fillers. These compositions can be cured under relatively mild conditions to produce elastomeric or resinous products depending on the type and relative concentrations of reactants present in the initial curable composition. can. The resulting cured product is useful for a variety of applications including encapsulation of precision electrical and electronic components, coating various substrates, as pressure sensitive adhesives, etc., and forming molded articles by injection molding. Useful.

Reinforcing fillers such as fume silica have been used to improve physical properties such as tensile strength, tear strength and modulus of cured polyorganosiloxane compositions.

The prior art teaches the use of resinous siloxane copolymers as a replacement for reinforcing silica fillers to improve the physical properties of cured polyorganosiloxanes while retaining the transparency of unfilled materials. In particular, 196
U.S. Patent No. 3 issued to Nelson on November 8, 2006
．． No. 284,406, U.S. Pat.
US Patent No. 4 issued to Modic on September 18, 1984
．． No. 472,470, all for this purpose,
iO+zz, 1hVisio+/z and S+04
The use of resinous copolymers containing zz units is disclosed. In the above formula, R represents a monovalent hydrocarbon group without an ethylenically unsaturated bond, and Vi represents a vinyl group.

The cured materials disclosed in the aforementioned Nelson and Modic patents typically exhibit hardness values of 35 to 80 on the Shore A durometer scale, indicating a relatively hard, highly crosslinked material. The Modic patent teaches the inclusion of finely divided non-reinforcing fillers when cured product transparency is not required.

The curing agents taught by Modic are liquid polyorganohydrogensiloxanes containing at least two silicon-bonded hydrogen atoms per molecule;
Contains silicon-bonded hydrogen atoms. Furthermore, Ne
1son composition contains 0.75 to 1.5 per vinyl group.
silicon-bonded hydrogen bonds, which is equivalent to a maximum of 1 to 3 vinyl groups per silicon-bonded hydrogen.

The tear strength of a cured polyorganosiloxane prepared from a liquid composition similar to that disclosed in the Nelson and Modic patent was determined by reducing the viscosity of the curable composition by 10.
A method of increasing the pressure while maintaining it within the range of ~500 Pa, s is described by Jeram and Smi on July 20, 1982.
No. 4,340,709, issued to th. According to the disclosure of this patent, 0.14 to 2
．． 100 parts by weight of a liquid polydiorganosiloxane containing 0 mol% diorganovinylsiloxy units is used in combination with a crosslinking agent and 75-150 parts of a "coupler" containing 3-9 mol% dimethylhydrogensiloxy units. and hardened. Those skilled in the art will be familiar with the term "chain extender".
Couplers, also referred to as (tender) J, are linear polydiorganosiloxanes containing a silicon-bonded hydrogen atom at each of the two terminal positions of the molecule and no additional silicon-bonded hydrogen. A crosslinking agent is defined as a linear hydrogenated polysiloxane containing hydrogen atoms only on non-terminal silicon atoms only in internal positions of each molecule or as a hydride resin with only terminal hydrogen atoms.

In accordance with the claims of the aforementioned Jeram and Sm1th patents, the highest molar ratio of vinyl groups to silicon-bonded hydrogen atoms occurs when the repeating units of the polydiorganosiloxane are dimethylsiloxane units, and the polymer has The fU acid product contains 75 parts by weight of coupler per 100 parts by weight of polydiorganosiloxane, and the coupler contains 3.0 mol% dimethylhydrogensiloxy. Contains units. Under these conditions, the composition contains 0.012 vinyl groups per silicon-bonded hydrogen atom. This vinyl group content is lower when silicon-bonded hydrogen atoms are present in the crosslinker.

It is therefore clear from the claims of the Jeram and Smlth patent that the compositions contain more moles of silicon-bonded hydrogen atoms than moles of vinyl groups.

The cured compositions exemplified by Jerao+ and Smi th exhibit hardness values of 21 to 43 on the Shore A durometer scale after curing for 1 hour at 100<0>C. Hardness values in this range are desirable for protective coatings, encapsulants and certain molded articles.

A chain extender containing two silicon-bonded hydrogen atoms per molecule is combined with a curing agent containing an average of at least three silicon-bonded hydrogen atoms per molecule to improve the tensile properties of the cured polyorganosiloxane elastomer. The concept used for
No. 3,697.473, issued to Manteer eL al.

Chain extenders are polydiorganosiloxanes in which each of the two end units contains a silicon-bonded hydrogen atom and there are no additional silicon-bonded hydrogens in the molecule.

Both the chain extender and curing agent contain a minimum of 10% available silicon-bonded hydrogen atoms and are the only source of silicon-bonded hydrogen atoms present in the composition.

The curable compositions described by Polsanteer et al. contain 0.75 to 1.5 silicon-bonded hydrogen atoms for each vinyl group present in the polydiorganosiloxane component. According to this teaching, the curable composition cannot contain more than 1.3 vinyl groups per silicon-bonded hydrogen atom.

This is the same limitation disclosed in the Nclson patent.

The elastomer exemplified by Polmanteer et al.
It shows a durometer value of 8.

Nelson, Modic, Jeram et al.
From the tensile properties and hardness values reported in the patents of Al and Polman-teer et al., it appears that the cured products exemplified in this prior art have the compressibility and hardness required for certain applications of polyorganosiloxane elastomers. It is shown that it exhibits no elasticity. One such use is
A flexible to position sensitive optical screen of the type disclosed in U.S. Pat.
uch position sensitive opt
ical 5clean) as a light transmitting part.

Pressure-sensitive optical screens and other forms of compressible waveguides (c
(impressible waveguide)
a cured noncellular elastomer that is transparent, exhibits minimal light attenuation, and that can be bent or otherwise deformed by applying an electrostatic or mechanical force to at least one surface of the article; layers are required. Polyorganosiloxane elastomers suitable for this application typically have a
It exhibits a durometer value of less than 0.00 and is a much softer material than that measured using the Shore A scale. Furthermore, the elastomer must be sufficiently elastic that it almost immediately returns to its original shape when the pressure that deformed it is removed, and that this pressure is repeatedly applied to the same area of the elastomer. It must be strong enough to resist puncture and/or tearing when removed. It is also essential that the properties of the initially cured elastomer, particularly its compressibility and elasticity, do not change substantially over time.

If one or more surfaces of the deformable optical waveguide are covered with a film or thin film, adhesion along this interface is
It must be sufficient to prevent separation between the two layers and consequent void formation.

The combination of said properties required for optically transparent and deformable optical waveguides is not disclosed with respect to prior art polyorganosiloxane elastomer compositions.

An optically clear, curable polyorganosiloxane composition containing a vinyl-terminated polydiorganosiloxane, a resinous organosiloxane copolymer containing units of dimethylvinylsiloxy, trimethylsiloxy, and 5i047, and two organohydrogensiloxanes. 198
U.S. Patent No. 4 issued to Kroupa on August 13, 2005
．． No. 535.141. One of the organohydrogensiloxanes is the Jeram and S++++ith
It corresponds to a proprietary chain extender and contains silicon-bonded hydrogen atoms only at the terminal positions of the substantially linear polydiorganosiloxane molecule.

The concentration of chain extender is equivalent to at least 1.6 times the concentration of silicon-bonded hydrogen atoms, ie, the number of vinyl groups present in the curable composition. Other organohydrogensiloxanes function as curing agents and contain an average of at least three silicon-bonded hydrogen atoms per molecule.

The inventors have discovered that the cured elastomers prepared using the compositions described in the Kroupa patents continue to become harder over time and eventually become harder under typical operating conditions for waveguides. We have found that this is worse than a completely satisfactory material for compressible optical waveguides because it becomes too hard to be compressed. This phenomenon is often accompanied by the generation of hydrogen gas bubbles that interfere with the optical properties of the waveguide. It is believed that gradual curing and hydrogen evolution is due to the reaction of silicon-bonded hydrogen atoms present in the elastomer with moisture.

Subsequent work has shown waveguides containing preferred elastomeric compositions having relatively low compressive strengths as disclosed in the Kroupa patent. As such, these materials are unable to withstand the repeated compression experienced by touch screens of the type described in the Kasday patent.

[Purpose of the invention]

The object of the present invention is to produce an optically transparent elastomer that can be cured by a hydrosilation reaction and is suitable for use as a light-transmitting component of a compressible optical waveguide.
It is an object of the present invention to provide polyorganosiloxane compositions that can be transported in liquid or pumped form.

[Structure of the invention and its effects]

The curable polyorganosiloxane compositions of the present invention contain at least one vinyl-terminated liquid polydiorganosiloxane, diorganovinylsiloxy, triorganosiloxy, and a resinous organosiloxane reinforcing agent containing units of Sto, on average per molecule. It consists of an organosiloxane curing agent containing at least three silicon-bonded hydrogen atoms, a diorganohydrogensiloxy-terminated polydiorganosiloxane as a chain extender, and a platinum-containing hydrosilation catalyst. The molar ratio of vinyl groups to silicon-bonded hydrogen atoms in the composition is greater than 1.5.

Cured elastomers prepared using the compositions of the present invention are compressible and elastic, exhibiting hardness up to 100 on the Shore OO durometer scale.

The present invention provides a curable composition that produces an optically transparent polyorganosiloxane elastomer, the composition having the following components: at least one liquid polydiorganosiloxane containing vinyl groups in each of the two terminal positions; B6 from 5 to about 40%, based on the total weight of the composition, of a triorganosiloxane of the general formula R"3SiO+zg; siloxy units, diorganovinylsiloxy units and 5i02 units of the general formula CIIz=CII(R"')2SiOtzz, where R/1 and R"' each contain from 1 to about 20 carbon atoms and ethylene monovalent hydrocarbon or halohydrocarbon group having no unsaturated bonds), and the molar ratio of the combination of triorganosiloxy units and diorganovinylsiloxy units to 5in2 units is 0.
．． 7 to 1,2 and containing 0.1 to 8% by weight of silicon-bonded vinyl groups; C. an organohydrogensiloxane crosslinker containing at least 3 silicon-bonded hydrogen atoms per molecule; , 10 to 10 of the silicon-bonded hydrogen atoms present in the D0 composition
a diorganohydrogensiloxy-terminated polydiorganosiloxane containing two silicon-bonded hydrogen atoms and an average of up to 50 diorganosiloxane units in one molecule in an amount sufficient to provide 85% and promote the curing of the E1 composition. the product obtained by homogeneously mixing a platinum-containing hydrosilation catalyst in an amount sufficient to .5 vinyl groups, provided that the combined concentration of silicon-bonded hydrogen in the curing agent and the diorganohydrogensiloxy-terminated polydiorganosiloxane is sufficient to cure the composition. .

The components of the curable composition of the present invention will be described in detail.

1. Polydiorganosiloxane The polydiorganosiloxane of the composition of the present invention has the general formula (wherein R represents a monovalent hydrocarbon group or a monovalent halohydrocarbon group, Vi represents a vinyl group, and n represents the degree of polymerization corresponding to a viscosity of 1 to about 40 Pa, s at 25°C. The group represented by R contains 1 to about 20 carbon atoms. A range of 1 to 10 carbon atoms is preferred in view of the availability of the corresponding monomers. Most preferably, R is methyl, phenyl or 3,3,3-1-lifluoropropyl, which are preferred due to the availability of the reactants typically used to prepare the polydiorganosiloxane. It is based on

The reaction mixture may contain a single polydiorganosiloxane component, or two or more polydiorganosiloxanes of different molecular weights may be present.

The inventors have investigated the physical properties of cured elastomers, in particular:
It has been found that elasticity and tear strength are improved by using a combination of high and low molecular weight polydiorganosiloxanes. In preferred embodiments, the low molecular weight is about 0.1 to about 3 Pa,s at 25°C.
High molecular weight ones have a viscosity of 20 to about 4 at 25°C.
It shows a viscosity of 0.

Without wishing to be bound by theory, it is believed that the improvements in physical properties observed using the preferred polydiorganosiloxane compositions described above result from changes in crosslink density in the cured elastomer. This concept will be explained in more detail later.

2. Resinous Organosiloxane Copolymers - Because the elastomers of the present invention must be optically transparent, solid reinforcement agents such as finely divided silica typically cannot be used. Instead, the necessary reinforcement is obtained by using from about 5 to about 40% of the resinous vinyl-containing organosiloxane copolymer described above, based on the weight of the curable composition used to prepare the elastomer. It will be done. These copolymers react during curing and are thereby incorporated into the structure of the final elastomer. We have found that less than about 5% by weight copolymer generally does not provide the necessary elasticity and toughness, whereas about 40% by weight
It is believed that a copolymer of more than There is. A more serious disadvantage of using too much resinous copolymer is an unacceptable reduction in the compressibility of the cured elastomer. Preferred elastomeric surfaces are bent by light or gentle finger pressure.

The resinous copolymer contains triorganosiloxy units of the general formula R''zsi017□ and of the general formula C1l□=Cfl
(R''') zS iO+ In addition to the diorganovinylsiloxy units of y□, it contains repeating units of the general formula SiO□.

In these formulas, RII and R'' are each a monovalent hydrocarbon or halohydrocarbon radical containing from 1 to about 20 carbon atoms, as defined above for the R group of the polydiorganosiloxane component. Yes, and both RH and R'' do not contain ethylenically unsaturated groups.

The molar ratio of triorganosiloxy units and diorganovinylsiloxy units to SiO□ units in the resinous copolymer is from 0.7 to 1.2 (inclusive).

Vinyl-containing units, preferably containing at least two vinyl groups per molecule, constitute 2-8% of the copolymer. In a preferred embodiment of the copolymer, diorganovinylsiloxy: triorganosiloxy: Sing
The molar ratio of units ranges from 0.08 to 0.1:0.06
~1:l.

The resinous copolymer was published by Daud on April 20, 1954.
U.S. Patent No. 2.67 issued to and Tyler
6,182. The copolymers described in this patent contain 2-23% by weight of hydroxyl groups, which is significantly higher than the maximum level of about 0.8% by weight preferred for the precursors of the copolymers of the present invention. The hydroxyl content of the precursor is Dau
Triorganosiloxane capping agents (ca
It can be conveniently reduced to the desired level by using a ppping agent).

Briefly, the method of Daudt et at consists of reacting silica hydrosil with a suitable amount of hexamethyldisiloxane or trimethylchlorosilane under acidic conditions. The resinous copolymers used to prepare the elastomers of the present invention are described by Daudt et al.
The product of It can be obtained by reacting with

To ensure compatibility of the reactants and transparency of the cured polyorganosiloxane elastomer, it is preferred that the silicon-bonded hydrocarbon groups present in the polydiorganosiloxane, curing agent, and resinous agent be the same. Most preferably, these hydrocarbon groups are methyl or a combination of methyl and phenyl or 3,3,3-trifluoropropyl, which are preferably used to prepare the polydiorganosiloxane. based on the availability of intermediates.

Margin 3 below: Curing agent and chain extender The polydiorganosiloxane component and resinous organosiloxane copolymer are cured to form an elastomer through a hydrosilation reaction with silicon-bonded hydrogen atoms present in the curing agent and chain extender. .

The curing agent contains from as few as 4 to an average of 20 or more silicon atoms per molecule and has a
, s or higher viscosity.

This component also contains at least three silicon-bonded hydrogen atoms per molecule. Repeating units that may be present in this component include, in addition to one or more of monoorganosiloxy, diorganosiloxy, triorganosiloxy and Sing units, H3iO+, s, R' H3
Although it contains iO and/or R' JSiO+, it goes without saying that it is not limited to these. In these formulas, R' is a monovalent hydrocarbon or halohydrocarbon group as defined above for the R group of polydiorganosiloxane. Alternatively, the organohydrogen siloxane is a cyclic compound containing diorganosiloxane and organohydrogen siloxane units or formula 5i (OSi
R' J)4 may be a compound. Most preferably, R
' is methyl, and the curing agent contains an average of 10 to about 50 repeating units per molecule, of which 3 to 5 are methylhydrogensiloxane, a linear trimethylsiloxy-terminated dimethylsiloxane/methylhydrogensiloxane copolymer. It is.

[
It is included in the composition of the present invention as a chain extender. The chain extender contains an average of up to 50 diorganosiloxane units and 2 silicon-bonded hydrogen atoms per molecule. This silicon-bonded hydrogen is located at the terminal position of the molecule.

Preferred chain extenders contain 10 to 50 dimethylsiloxane units per molecule. Chain extenders of this type are known, for example, from p01mantee on October 10, 1972.
No. 3,697, issued to ret.
, No. 473.

Chain extenders provide 10-85% of the silicon-bonded hydrogen atoms present in the curable compositions of the present invention.

Preferably, this range is from 30% to about 70% and the chain extender is a dimethylhydrogensiloxy terminated polydimethylsiloxane.

The molecular weight of the polydiorganosiloxane and curing agent, along with the number and distribution of silicon-bonded hydrogen atoms and vinyl groups in the reactants used to prepare the elastomer,
Determine the location of crosslinks in the cured material. The concentration of crosslinks per unit area is often referred to as the “crosslink density”;
Certain physical properties of cured elastomers, particularly hardness,
Determine compressibility and elasticity. Polydiorganosiloxanes that provide an optimal combination of these physical properties
The particular combination of curing agent(s), and resinous organosiloxane copolymer can be readily determined by routine experimentation with the knowledge of the present invention.

The molar ratio of vinyl or other ethylenically unsaturated hydrocarbon groups to silicon-bonded hydrogen atoms and the relative concentration of silicon-bonded hydrogen in the curing agent and chain extender are critical with respect to the properties of the cured elastomer. The compositions of the invention include at least 1 silicon-bonded hydrogen atom.
．． Contains 5 vinyl or other ethylenically unsaturated hydrocarbon groups. The optimal ratio of vinyl groups to silicon-bonded hydrogens required to obtain a cured elastomer exhibiting the desired combination of compressibility, toughness, and elasticity depends, at least in part, on the molecular weight of the polydiorganosiloxane(s);
Determined by the type of curing agent and the concentration of resinous organosiloxane copolymer.

It is understood that the concentration of vinyl groups to silicon-bonded hydrogen atoms should not exceed a value such that the composition does not cure to produce a useful material exhibiting the properties described above.

This value is typically about 10 moles of vinyl groups per mole of silicon-bonded hydrogen. The compositions of the invention preferably contain 2 to 4 moles of vinyl groups per mole of silicon-bonded hydrogen atoms.

It should be understood that allyl or other ethylenically unsaturated hydrocarbon groups may partially or completely replace the vinyl group.

4. Platinum-Containing Catalyst and Optional Inhibitor Hydrosylation reactions are typically carried out in the presence of a catalyst that is a platinum group metal or a compound of the metal. Platinum compounds such as hexachloroplatinic acid and especially complexes of these compounds with relatively low molecular weight vinyl-containing organosiloxane compounds are preferred catalysts because of their high activity and affinity with organosiloxane reactants. These complexes are
December 31, 1968 David N. Willin
No. 3,419,593, issued to G.G.

Complexes having low molecular weight organosiloxanes in which the silicon-bonded hydrocarbon groups are either vinyl and methyl or 3.3.3-)lifluoropropyl catalyze rapid curing of elastomers at temperatures of at least about 70°C. It is particularly preferred because of its effectiveness.

The platinum-containing catalyst may be present in an amount equivalent to as little as 1 part by weight (1 ppm) of platinum per million parts of the curable composition. 5 to 50 parts of platinum per million parts of curable composition (5 to 50 parts)
A catalyst concentration equivalent to 50 ppm) is preferred to achieve practical cure rates. Concentrations of platinum higher than this provide only insubstantial cure rate improvements and are therefore economically unattractive, especially when the preferred catalysts are used.

The mixture of vinyl-containing reactant, curing agent, chain extender, and platinum-containing catalyst begins to cure at room temperature. In order to increase the storage stability of these compositions or obtain a longer working time or "pot life", the activity of the catalyst under normal conditions can be retarded or suppressed by the addition of suitable inhibitors.

Known platinum catalyst inhibitors include Ko
Included are the acetylene compounds disclosed in U.S. Pat. No. 3,445,420, issued to Okootsedes et al. Acetylene alcohols such as 2-methyl-3-butyn-2-ol constitute a preferred type of inhibitor that suppresses the activity of platinum-containing catalysts at 25°C. Compositions containing these catalysts typically require heating to temperatures of 70° C. or higher to cure at practical rates.

If it is desired to increase the pot life of curable compositions under normal conditions, this can be done using the techniques described in U.S. Pat.
This can be accomplished using olefinically substituted siloxanes of the type described in No. 989,667. Cyclic methyl and nylsiloxanes are preferred.

Inhibitor concentrations as low as 1 mole of inhibitor per mole of platinum provide acceptable storage stability and cure speed in some instances. Other examples require inhibitor concentrations of up to 500 moles of inhibitor per mole of platinum or more. The optimal concentration of a given inhibitor in a given composition can be readily determined by routine experimentation and does not form part of this invention.

Below, Margin 5, Properties of the curable composition and cured elastomer The curable composition containing each of the components described so far is as follows:
It typically exhibits a viscosity of up to 100 Pa, s at 25 °C. To facilitate mixing and transfer of the composition and to minimize air entrapment during mixing, at 25°C.
A viscosity of 5 to 10 Pa,s is preferred.

Cured polyorganosiloxane elastomers prepared using the compositions of the present invention typically range from 5 to It exhibits a hardness value of approximately 100.

Cured elastomers prepared using the polyorganosiloxane compositions of the present invention are optically clear and can be molded, molded, or molded using conventional methods for processing liquid or pumpable polyorganosiloxane compositions. Suitable for manufacturing articles by casting or other techniques. Elastomers exhibiting hardness values of 5 to about 40 are particularly suitable materials for the light-transmitting portion of the optical waveguide. Because of the physical properties of these preferred elastomers, particularly their compressibility, toughness, and elasticity, these elastomers are well suited for use in U.S. Pat.
484.179.
tion 5eusi-tive 5clean).

〔Example〕

The following examples disclose preferred curable compositions of the present invention, and it goes without saying that the technical scope of the present invention is not limited to these examples. Example 2 is
Prior art compositions containing components similar to those of the present invention, except that a stoichiometric excess of silicon-bonded hydrogen atoms is present in place of the stoichiometric excess of vinyl groups that characterize the compositions of the present invention. to indicate the gradual hardening that characterizes something,
Included for comparison purposes. All parts and percentages disclosed in the following examples are by weight unless otherwise specified.

Below, 1. White Flame The compressibility and elasticity of elastomers prepared using the preferred curable compositions of the present invention were determined on November 20, 1984.
U.S. Patent No. 4.484,1 issued to Kasday
by incorporating the elastomer into a contact position sensing optical waveguide of the type disclosed in No. 79.

A curable composition was prepared by mixing the following materials to form a homogeneous mixture.

Approximately 2. 56.0 parts of dimethylvinylsiloxy endblocked polydimethylsiloxane (component 1'') having a viscosity of I Pa,s.

Dimethylvinylsiloxy-terminated polydimethylsiloxane (component 11) having a viscosity of about 30 Pa, s at 25°C
44.0 parts; Triorganosiloxy units and SiO2 units are converted into SiO
2 units per mole of triorganosiloxy units, the triorganosiloxy units are trimethylsiloxy units and dimethylvinylsiloxy units, and the resinous copolymer contains 4 to 2.2% by weight per mole of triorganosiloxy units. 45.2 parts of benzene-soluble resinous copolymer containing silicon-bonded vinyl groups (component III); 7.85 parts of dimethylhydrogensiloxy-terminated polydimethylsiloxane containing an average of 20 dimethylsiloxane units per molecule; Q, 3 Pa 2.94 parts of a trimethylsiloxy-terminated dimethylsiloxane/methylhydrogen siloxane copolymer (component IV) having a viscosity of , s and containing 0.16% by weight of silicon-bonded hydrogen atoms (component IV); sufficient to provide 0.7% by weight of platinum. Hexachloroplatinic acid complex of divinyltetramethyldisiloxane diluted with an amount of liquid dimethylvinylsiloxy-terminated polydimethylsiloxane (component ①) 0.
3 parts: and 0.2 parts of cyclic methylvinylsiloxane oligomer (component VI) as platinum catalyst inhibitor.

The resulting curable composition contained 2.23 vinyl groups for each silicon-bonded hydrogen atom.

The curable composition was poured into an erected container made by tightening three of the four joined edges of two overlapping sheets of polyurethane film. Polyurethane is [! s Lane (registered trademark) 58
Available as 87. The sheet had a size of 45 cm x 47 aa and a thickness of 0.5 mm.

The inner walls of this vessel were pre-filled with 120 g of dry methylene chloride, 13.5 g of trimethylsiloxy-terminated polymethyl chloride having a viscosity of about 0.13 Pa, s at 25° C. and a silicon-bonded hydrogen atom content of about 1.6% by weight. Coated with a primer solution prepared by combining hydrogen siloxane, and a hexachloroplatinic acid complex of divinyltetramethyldisiloxane diluted with dimethylvinylsiloxy-terminated polydimethylsiloxane to give 0.7% by weight platinum. I kept it. “The filled container was then tightly sandwiched between two plates separated by a 3.2 mm spacer, maintaining the container in a substantially vertical position, and the entire assembly was placed in an oven heated to a temperature of 66°C. I placed it inside.

After heating for 30 minutes to harden the composition into an elastomer, the set 1 was taken out of the oven.

18.3cm x 23.4c from a hardened elastomer container
A rectangular section of size n was cut to form an optical waveguide. The exposed elastomer layer on the outer periphery of the waveguide is
The waveguide was coated using the same solution used to coat the prepared film.

The waveguide was then heated at a temperature of 66° C. for 1 hour to cure the coating and fully cure the elastomer.

When cured for 20 minutes at a temperature of 150 DEG C. without a polyurethane film, the elastomer exhibited a hardness of 11 on the Shore 00 durometer scale. The final optically transparent waveguide is 4.6 mm thick and a 1.63 diameter spherical foot is used to recess the surface of the waveguide a distance M1. 117g in
It was necessary to add force. The waveguide took less than 1 second to remove this force and return to its original thickness.

The compressive strength of the waveguide is measured by determining the force required to break the surface of the waveguide using a 1.6 cm diameter spherical foot. This person weighed 17.6 kg.

The waveguides were then subjected to an aging test by heating them at 66° C. for 46 days to determine the effect on the compressibility of the waveguides. After 14 days, the distance of the surface of the waveguide is 1! ! t1. The force required to compress by 0 mm was 123 g. After 49 days, this force will be 13
increased to 0g. This represented a 5% increase from the original value.

This example demonstrates the gradual irreversible cure exhibited by elastomers prepared using prior art curable compositions containing a stoichiometric excess of silicon-bonded hydrogen atoms. This composition is one of those disclosed in US Pat. No. 4,535,141, issued Aug. 13, 1985 [roupa.

The outer portion of the optical waveguide was formed by heat sealing a sheet of polyurethane film as described in Example 1 above to both sides of a rectangular frame made of the same material.

The inside dimensions of the frame were 16.4 cm x 21°3 cm, and the thickness of the frame was 0.5 am. The surface of the film forming the inner wall of the container was coated with the primer solution of Example 1 along all edges where the film was in contact with the frame. The resulting container was filled with a curable composition prepared by mixing together the following materials to form a homogeneous mixture.

100 parts of a mixture of three dimethylvinylsiloxy-terminated polydimethylsiloxanes identified as a, b and C, polydimethylsiloxane a comprising 35% by weight of the mixture and exhibiting a viscosity of about 2 Pa,s at 25°C; Polydimethylsiloxane b constitutes 52% by weight of the mixture and is
and polydimethylsiloxane C constitutes the remaining 13-layer compound of the mixture, with a viscosity of about 30 Pa, s.
19 parts of the benzene-soluble resinous copolymer described in Example 1 above; an average of 5 methylhydrogensiloxane units and 3 dimethylsiloxane units per molecule; 0.7~0
．． 0.7 parts of a crosslinking agent consisting essentially of a trimethylsiloxy-terminated dimethylsiloxane/methylhydrogensiloxane copolymer having a silicon-bonded hydrogen atom content in the range of 8% by weight; a dimethylhydrogensiloxy-terminated polydimethylsiloxane as described in Example 1 above; 28 parts; 0.18 parts of the platinum-containing hydrosilation catalyst described in Example 1; and 0.26 parts of cyclic methylvinylsiloxane oligomer as catalyst inhibitor.

The resulting composition contained 0.3 per silicon-bonded hydrogen atom.
It contained 65 vinyl groups. the filled container,
Sandwiched tightly between two plates separated by a 0.5 ca+ thickness spacer, the entire assembly was left to cure into an elastomer at room temperature for 8 hours, then post-cured for 2 hours in an open air maintained at 66°C. Ta.

The cured product was an optically clear waveguide approximately 50 mm thick and required 55 g of force to indent the surface a distance of 1 mm. This waveguide was subjected to the accelerated hardness test described in Example 1 above. After 7 days, the force required to indent the waveguide surface increased to 110 g. After 28 days this will be 40
0g, an increase of 727% from the initial value. The need to apply this amount of force to concave the surface of a touch-sensitive optical waveguide of the type described in the Kasday patent mentioned in the previous part of this specification makes it difficult for potential users of the waveguide to is not acceptable.

This example demonstrates the relatively low compressive strength exhibited by cured elastomers prepared using curable compositions that exclude the chain extender component of the compositions of the present invention.

A curable composition was prepared by mixing the following amounts of components (1) to (2) defined in Example 1 above to obtain a homogeneous mixture.

Bottom of margin below - Light Part 1 II 43 III 46 ■7.7 VO, 3 VI 0.2 The molar ratio of vinyl groups to silicon-bonded hydrogen atoms in this curable composition was 3.0.

Samples of the composition were cured by heating outside the container at 150° C. for 20 minutes. The durometer hardness of this cured elastomer was 20 on the Shore 00 scale.

A waveguide was prepared using the method described in Example 1 above and using this curable composition with a polyurethane film. The compressive strength of the subsequently post-cured waveguide was 6.75 kg, compared to 17.6 kg for the waveguide described in Example 1 above prepared using a curable composition containing a chain extender. Met.

Margin below

Claims (1)

[Claims] 1. The composition contains the following components: A. At 25°C, the pressure is 0.1 to 40 Pa. at least one liquid polydiorganosiloxane having a viscosity of s and containing vinyl groups in each of the two terminal positions; ``_3SiO_1_/_2 triorganosiloxy unit, general formula CH_2=CH(R''')
_2SiO_1_/_2 diorganovinylsiloxy units and SiO_2 units (in the above formula, R″ and R″′
are monovalent hydrocarbon or halohydrocarbon radicals each containing from 1 to about 20 carbon atoms and having no ethylenically unsaturated bonds), consisting essentially of triorganosiloxy units and di- The molar ratio of the combination of organovinylsiloxy units is 0.7 to 1.2, and 0.7 to 1.2.
a benzene-soluble resinous copolymer containing 1 to 8% by weight of silicon-bonded vinyl groups; C. an organohydrogensiloxane curing agent containing at least 3 silicon-bonded hydrogen atoms per molecule; D. silicon present in the composition. 10~ of bonded hydrogen atoms
E. a diorganohydrogensiloxy-terminated polydiorganosiloxane containing two silicon-bonded hydrogen atoms and an average of up to 50 diorganosiloxane units in one molecule in an amount sufficient to provide 85% curing of the composition. and the composition contains at least 1.5 vinyl groups for each silicon-bonded hydrogen atom. and wherein the combined concentration of the curing agent and the diorganohydrogensiloxy-terminated polydiorganosiloxane is sufficient to cure the composition. 2. The vinyl-containing polydiorganosiloxane has a general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (In the formula, R represents a monovalent hydrocarbon group or a monovalent halohydrocarbon group, and Vi represents a vinyl group. , n represents a degree of polymerization corresponding to a viscosity of from 0.1 to about 40 Pa.s at 25°C. 3, R represents a monovalent hydrocarbon or halogenated hydrocarbon group containing 1 to 10 carbon atoms, and the organohydrogensiloxane is HSiO_1_. _5, R'HSi
O and R′_2HSiO_0_. Contains at least 3 repeating units per molecule selected from the group consisting of __5 (wherein R' represents a monovalent hydrocarbon or halogenated hydrocarbon group containing 1 to 10 carbon atoms) , and the remaining repeating units are monoorganosiloxane, diorganosiloxane, triorganosiloxy and SiO
The composition of claim 2 selected from the group consisting of _2. 4. The viscosity of the composition is 100 Pa. at 25°C. R, R', R'' and R''' are methyl,
4. A composition according to claim 3, which is phenyl or 3,3,3-trifluoropropyl. 5. Dimethylsiloxane in which R, R', R'' and R'' are methyl and the curing agent contains on average 10 to 50 repeating units and 3 to 5 silicon-bonded hydrogen atoms per molecule; methylhydrogensiloxane copolymer, the composition contains 2 to 4 moles of vinyl groups per mole of silicon-bonded hydrogen atoms, the silicon-bonded hydrocarbon groups of the diorganohydrogensiloxy-terminated polydiorganosiloxane are methyl, and the platinum 5. The composition of claim 4, wherein the hydrosilation catalyst contained is a reaction product of hexachloroplatinic acid and a vinyl-containing organosiloxane compound. 6. The composition contains two types of the liquid polydiorganosiloxane, the first one having a temperature of 0.1 to 3 Pa. at 25°C. The second one has a viscosity of 20-40 Pa.s at 25°C. s
6. The composition of claim 5, wherein the dimethylhydrogensiloxy-terminated polydimethylsiloxane contains 30 to 70 mole percent of the silicon-bonded hydrogen atoms present in the composition. 7. The composition according to claim 6, which contains a platinum catalyst inhibitor. 8. The composition according to claim 7, wherein the platinum catalyst inhibitor is acetylene alcohol.