KR20100058307A - Silicone rubber composition for preparing silicone blanket - Google Patents

Abstract

PURPOSE: A silicone rubber composition is provided to improve the lifetime and printability of a blanket while offset printing and to enhance the swelling property of the blanket by being comprised of polymer polysiloxane hydride. CONSTITUTION: A silicone rubber composition for manufacturing a silicone blanket contains 50~95wt% of polysiloxane for the total amount of the composition. The composition also contains 5~25 parts of polymer polysiloxane hydride by weight with an average molecular weight of 3,000~10,000 and 0.1~3 parts of silica by weight based on 100 parts of polysiloxane by weight. The polymer polysiloxane hydride has a structure marked as chemical formula 3: R3_cSiO_(4-c)/2. In chemical formula 3, R3 is an alkyl group with hydride groups on both ends. C is a positive number of 1.9~2.05.

Description

Silicone rubber composition for the manufacture of silicone blankets {SILICONE RUBBER COMPOSITION FOR PREPARING SILICONE BLANKET}

The present invention relates to a silicone rubber composition for producing a silicone blanket for use in micro pattern offset printing.

In general, offset printing is a method in which a paint image is transferred to a surface of a blanket rubber sheet on a pattern roll or plate, and the paint image of the blanket is transferred to a print object and printed indirectly. Therefore, in the offset printing plate, the image is the same as the original, the image of the blanket is vice versa, and on the print object, the image appears again as the original. At this time, when printing with an offset printing machine, the paint on the pattern roll or plate is initially transferred to the blanket, so it is called off and the paint on the blanket is buried again on the printing object.

Here, when the paint is on the blanket, a small amount of solvent in the paint penetrates into the blanket rubber plate, which swells the blanket rubber plate. As the number of prints increases, the swelling of the blanket rubber sheet gradually progresses, and the life of the blanket rubber sheet is regarded as the end of the life of the blanket rubber sheet when the swelling no longer progresses and the paint on the blanket does not proceed in the three stages.

Rubber blankets for offset printing use a variety of synthetic rubbers, typically styrene butadiene rubber, acrylonitrile butadiene rubber, butyl rubber, ethylene-propylene diene rubber, polybutadiene rubber, polychloroprene rubber, polyisoprene rubber, and silicone rubber. Etc. can be mentioned.

However, when printing with the rubber blanket used for such conventional offset printing, the print quality was not good and the micro-pattern could not be printed under various conditions. In particular, in the case of a silicone blanket with a high swelling degree of swelling in order to increase the service life, the initial swelling degree is rapidly increased, so that the paint is partially dried in the set process, and thus the initial print quality is not good. It may also generate a large amount of bumps in the result.

Accordingly, an object of the present invention is to provide a silicone rubber composition for producing a silicone blanket for micro pattern offset printing, which has a long life and excellent initial print quality.

According to the above object, the present invention comprises 50 to 95% by weight of polysiloxane, based on the total weight of the composition; On the basis of 100 parts by weight of the polysiloxane, 5 to 25 parts by weight of a polymer polysiloxane hydride having a weight average molecular weight of 3,000 to 10,000, and 0.1 to 3 parts by weight of silica, to provide a silicone rubber composition for producing a silicone blanket.

The present invention also provides a silicone blanket for micro pattern offset printing, which is obtained by thermal curing or UV curing the silicone rubber composition.

The silicone rubber composition for micro-pattern offset printing of the present invention uses polymer polysiloxane hydride to increase the swelling degree of the blanket to increase the printability and the blanket life during offset printing, while the addition of silica improves the tensile strength and the initial swelling speed. The initial print quality is improved because is adjusted.

Hereinafter, the composition of the present invention will be described in detail for each component.

Polysiloxane

The high vinyl polysiloxane serves to lower the viscosity and increase the hardness, and the high vinyl polysiloxane used in the present invention has a vinyl group content of about 0.1 to 0.4 mmol / g, and preferably a viscosity when measured by a Brookfield viscometer. It is 200-2,000 cPs, and it is preferable to have a structure of following formula (1).

R ¹ _a SiO _{(4-a) / 2}

Wherein R ¹ is a C ₂ -C ₁₀ alkenyl group and a is a positive number from about 1.9 to 2.05.

The low vinyl polysiloxane serves to increase the viscosity and swelling degree, and the low vinyl polysiloxane used in the present invention has a vinyl group content of about 0.01 to 0.1 mmol / g, and a viscosity as measured by a Brookfield viscometer is preferably about 2,000. It is preferably from 200,000 cPs, and has a structure of formula (2).

R ² _b SiO _{(8-b) / 2}

Wherein R ² is a C ₂ -C ₁₀ alkenyl group and b is a positive number from about 1.2 to 4.8.

High vinyl and low vinyl polysiloxanes are included in amounts ranging from about 50 to 95 weight percent based on the total weight of the silicone blanket rubber composition of the present invention, wherein the ratio of high vinyl polysiloxanes to low vinyl polysiloxanes is from 1: 1 to 1. It is preferable that it is a weight ratio of 2 :. If the high vinyl polysiloxane is higher than the above content, the silicone rubber may become hard, and if less, the silicone rubber to be formed may be easily brittle. In addition, when the low vinyl polysiloxane is less than the above content, the tensile strength of the silicone rubber may be weakened, and when it is more, the viscosity may be high, thus making it difficult to manufacture the silicone rubber sheet.

Polymeric Polysiloxane Hydride

The polysiloxane hydride acts as a binder and is activated by a catalyst to destabilize the π bond of vinyl polysiloxane and to bind it. In particular, the polymer polysiloxane hydride in the present invention serves to improve the swelling characteristics of the blanket. Polymeric polysiloxane hydrides have a weight average molecular weight of about 3,000 to 10,000 And it is preferable to have a structure of following formula (3).

R ³ _c SiO _{(4-c) / 2}

Wherein R ³ is a C ₁ -C ₁₀ alkyl group having hydride groups at both terminal sites, and c is a positive number from about 1.90 to 2.05.

The polysiloxane hydride polymer is preferably included in an amount of about 5 to 25 parts by weight relative to 100 parts by weight of polysiloxane, wherein if the content is less than 5 parts by weight, the crosslinking degree may be poor and hardening may not proceed or surface stickiness may occur. If it exceeds 25 parts by weight, the length of the crosslinked polymer chain may be short, resulting in poor physical properties. For the same reason, it is preferable to set the number ratio of the vinyl group and the hydride group to be about 1: 1 to 1: 4.

Silica

In the silicone blanket rubber composition of the present invention, silica is added in powder form to improve initial print quality. Silica preferably has a specific surface area (BET) of 100 to 400 m 2 / g and a tapped density of 30 to 70 g / L. As a compound having SiO ₂ of 90% by weight or more, crosslinking proceeds to the upper layer during curing, thereby lowering the initial solvent absorption rate. That is, by adding silica, the physical property of the upper part of the silicone blanket is modified, and the initial swelling speed is controlled during offset printing. Thus, tearing during initial printing can be improved, and the role as a blanket rubber and print quality can be further improved. . In addition, the mechanical properties are improved to prepare for a myriad of contacts between the gravure pattern roll and the glass substrate.

Platinum catalyst

In the silicone blanket rubber composition of the present invention, a platinum catalyst may be added in powder form to activate the curing reaction. The amount of the platinum catalyst is preferably included in an amount ranging from about 10 to 50 ppm by weight relative to 100 parts by weight of the composition. If the content is less than 10 ppm by weight, the curing may not proceed well at a high temperature and exceeds 50 ppm by weight. Hardening can proceed at room temperature.

Polymerization inhibitor

In accordance with the present invention, it is preferred that the silicone blanket rubber composition containing the platinum catalyst contains an polymerization inhibitor. This is because curing of the composition can proceed rapidly at room temperature due to the excellent reactivity of the added platinum catalyst. The polymerization inhibitor to be used may be any conventionally used in the art, and specific examples thereof include phosphoric acid, formic acid and methane sulfonic acid; Examples of the substance include a methyl group, a vinyl group, or a phenyl group, such as methanol and 2,6-di- t- butyl-4-methyl-phenol, but are not limited thereto. The addition amount of the polymerization inhibitor is preferably included in an amount of about 0.5 to 2 parts by weight relative to 100 parts by weight of the composition, but if the content exceeds 2 parts by weight, the curing may not proceed at high temperatures.

The silicone blanket rubber composition containing the above components may be prepared in a silicone blanket having one of a bulk molding compound (BMC) form or a sheet molding compound (SMC) form.

The BMC form is mixed and stirred to form a dough-like state to be injected into the mold or placed in the lower side of the inside of the mold during compression molding, for example, 50 to 160 kg / ㎠ at a temperature of 50 to 160 ℃ It is pressurized for a certain time according to the target thickness by pressure and heat cured or UV cured to produce a thermosetting synthetic resin molded article of a desired shape, that is, a silicone blanket.

SMC form is prepared by mixing and stirring the composition and then packaging with a protective film for aging for a certain time (aging). A thermosetting synthetic resin molded article of a desired shape, that is, a silicone blanket, is pressed into a mold into which an SMC form is injected, for example, at a temperature of 50 to 160 ° C. at a pressure of 50 to 160 kg / cm 2 for a predetermined time, and thermally cured or UV cured. Will produce.

The silicone blanket of the present invention not only has excellent curing and printing properties, but also maximizes swelling properties and resilience while reducing hardness by using a polymer polysiloxane hydride, and also by adding silica, physical properties of the upper part of the silicone blanket are modified. Since the initial swelling speed is controlled during offset printing, the tearing phenomenon during the initial printing is improved, and the role of the blanket rubber and the printing quality are further improved.

The following will be described in more detail with reference to embodiments of the present invention. However, the following examples are merely examples of the present invention and the scope of the present invention is not limited thereto.

Preparation of the ingredients

The material used for the following Example of this invention was prepared as follows.

1) high vinyl polysiloxane: AB109358, ABCR chemical company, viscosity = 800 cPs, vinyl content = 0.1 mmol / g, Structural Formula- R ¹ _a SiO _{(4-a) / 2} (R ¹ = C ₃ alkenyl, a = 2.1)

2) Low Vinyl Polysiloxane: AB109361, ABCR Chemical, Viscosity = 120,000 cPs, Vinyl Content = 0.03 mmol / g, Structural Formula- R ² _b SiO _{(8-b) / 2} (R ² = C ₉ alkenyl, b = 3.3 )

3) Polymeric polysiloxane hydride: AB109368, ABCR chemical company, Mw = 6,000, hydride content = 1.1 mmol / g , formula-R ³ _c SiO _{(4-c) / 2} (R ³ = C ₉ alkyl, c = 1.95 )

4) Low molecular polysiloxane hydride: AB109365, ABCR chemical company, Mw = 2,000, hydride content = 2.1 mmol / g, structural formula-R ³ _c SiO _{(4-c) / 2} (R ³ = C ₃ alkyl, c = 1.95 )

5) Silica: Aerosil 200, EVONIC, Specific Surface Area: 200 ㎡ / g, Compression Density 50 g / L

6) Polymerization inhibitor: AB108801, ABCR chemical company

7) Platinum catalyst: AB121421, ABCR chemical company, purity: 80 ~ 81%

Comparative Examples 1 and 2: Preparation of Silicone Rubber Compositions

High-vinyl polysiloxane and low-vinyl polysiloxane were added to a 250 ml container, followed by stirring for about 10 minutes at 2000 rpm in a stirrer Dispermat. A polymer or a low molecular polysiloxane hydride was added thereto, a polymerization inhibitor was added thereto, followed by stirring at 2000 rpm for about 10 minutes. Subsequently, a platinum catalyst was added, mixed for 5 minutes in an ARE-250 mixer, and degassed for 5 minutes to prepare various liquid silicone rubber compositions having the composition shown in Table 1 below.

Examples 1 to 3: Preparation of Silicone Rubber Compositions

In addition to the high-vinyl polysiloxane and low-vinyl polysiloxane in a 250 ml container, silica was added in varying amounts of addition and stirring was carried out in the same manner as in Comparative Examples 1 and 2, and the composition shown in Table 1 below. Various liquid silicone rubber compositions were prepared.

Test Example

Test Example 1 Evaluation of Physical Properties According to Composition of Silicone Blanket Rubber

1. Fabrication of Silicone Blankets

Each of the liquid silicone rubber compositions prepared in Comparative Examples and Examples was coated on one side of a polyethylene (PET) film by using an applicator (applicator) to a thickness of 500 ㎛ 10 in a 70 ℃ convection oven (convection oven) Degassed for minutes and allowed to cure for 20 minutes in a 150 ° C convection oven to prepare each silicone blanket specimen.

2. Measurement of physical properties

The test method in this test example is as follows.

1) Evaluation of the swelling characteristics of the solvent-Each of the prepared silicone blanket cured to a thickness of 500 ㎛ to 10 x 10 ㎝ size to contact the high boiling point solvent BC (butylcellusolve) for 30 minutes and then swell through the weight change The properties were evaluated.

2) Tensile strength measurement-Each of the prepared silicone blanket cured to a thickness of 500 ㎛ cut to 1 cm tensile strength was measured using an Instron 4443 model, Universal Testing Machine (UTM).

3) Hardness Measurement-Hardness was measured using Mitutoyo's HH-336 (Type A).

4) Viscosity Measurement-The viscosity of each liquid silicone rubber composition prepared in Comparative Examples and Examples was measured using Brookfield RVDVII +.

3. Evaluation of Physical Properties by Addition of Polysiloxane Hydride by Type

The physical properties of the silicone blankets prepared by curing the compositions of Comparative Examples 1 and 2 prepared by adding different kinds of polysiloxane hydride under the same conditions were measured.

From Table 2, it can be seen that the use of the polymer polysiloxane hydride (Comparative Example 2) is more excellent than the case of using the low molecular polysiloxane hydride (Comparative Example 1).

4. Evaluation of physical properties according to the amount of silica added

Physical properties of the silicone blankets prepared by curing the compositions of Examples 1 to 3 added with varying amounts of silica were measured.

In Table 3, when the silica was added (Examples 1 to 3), the tensile strength was increased compared to the case where the silica was not added (Comparative Examples 1 and 2 of Table 2), and also in proportion to the amount of silica added. It was found that the tensile strength increased and the swelling decreased.

5. Evaluation of Saturation Swelling Characteristics

Saturation swelling properties were evaluated for each silicone blanket prepared using the silicone rubber compositions of Comparative Example 1, Comparative Example 2 and Example 1. The measurement method measured the BC swelling measurement method of Test Example 2 at 20 minute intervals to evaluate the swelling according to the solvent contact time. The results are shown in FIG.

In view of this, the case of using the polymer polysiloxane hydroxide (Comparative Example 2 and Example 1) than the case of using the low molecular weight polysiloxane hydroxide (Comparative Example 1) had significantly superior swelling characteristics Could know.

In Comparative Example 2 and Example 1, the maximum saturation swelling degree was the same, but the initial swelling degree was relatively high in the curve when silica was not added (Comparative Example 2). In this case, the initial print quality may be degraded due to excessive absorption of the solvent. On the other hand, when the silica is added (Example 1), it can be seen that the initial swelling degree is smooth. As described above, in the case of Example 1, the maximum saturation degree of swelling is high, and thus the initial swelling degree is smooth while the initial swelling degree is excellent.

Test Example 2 Evaluation of Initial Printing Quality with or without Silica

Under the same conditions, offset printing was performed using a silicone blanket prepared by curing the composition (Comparative Example 2) prepared without adding silica and the composition prepared by adding silica (Example 1) as described above. The fine patterns formed on the printing paper at the time of five printing are shown in Figs. 1A and 1B, respectively.

In this case, when the silica is not added (FIG. 1A), the printing state is poor, such as uneven shape of the fine pattern, and projections are generated. On the other hand, when silica is added (FIG. 1B), fine quality printed matter can be obtained. there was. If the initial swelling degree is excessive, the solvent of the paint is initially excessively absorbed to lower initial print quality. On the other hand, the initial swelling degree is maintained at an appropriate level as silica is added.

In the above, the present invention has been described with reference to the above embodiments, which are only examples, and the present invention is attached to various modifications and other embodiments that are obvious to those skilled in the art. It should be understood that it can be performed within the scope.

1A and 1B are diagrams showing fine pattern results of offset printing using silicon blankets of Comparative Examples 2 and 1, respectively;

2 is a graph showing the swelling characteristics of the silicone blanket according to Comparative Examples 1, 2 and Example 1.

Claims (8)

50-95 weight percent polysiloxane, based on the total weight of the composition; Based on 100 parts by weight of the polysiloxane, 5 to 25 parts by weight of a polymer polysiloxane hydride having a weight average molecular weight of 3,000 to 10,000, and 0.1 to 3 parts by weight of silica, silicone rubber composition for producing a silicone blanket. The method of claim 1, The polymer polysiloxane hydride has a structure of the following general formula (3), silicone rubber composition: (3) R ³ _c SiO _{(4-c) / 2} Wherein R ³ is a C ₁ -C ₁₀ alkyl group having hydride groups at both terminal sites, and c is a positive number from about 1.9 to 2.05. The method of claim 1, The silicon rubber composition, characterized in that the specific surface area (BET) of the silica is 100 to 400 m 2 / g, and the tapped density is 30 to 70 g / L. The method of claim 1, The polysiloxane is a high vinyl polysiloxane of the general formula (1) having a vinyl group content of 0.1 to 0.4 mmol / g and a low vinyl polysiloxane of the general formula (2) having a vinyl group content of 0.01 to 0.1 mmol / g of 1: 1 to 1: 2 Silicone rubber composition, characterized in that it comprises by weight: [Formula 1] R ¹ _a SiO _{(4-a) / 2} Wherein R ¹ is a C ₂ -C ₁₀ alkenyl group and a is a positive number from 1.9 to 2.05; [Formula 2] R ² _b SiO _{(8-b) / 2} Wherein R ² is an alkenyl group of C ₂ -C ₁₀ , b is a positive number from 1.2 to 4.8. The method of claim 4, wherein The viscosity of the high vinyl polysiloxane is 200 to 2,000 cPs, the viscosity of the low vinyl polysiloxane is characterized in that the silicone rubber composition, 2,000 to 200,000 cPs. The method of claim 1, The number ratio of the vinyl group and the hydride group in the silicone rubber composition is 1: 1 to 1: characterized in that the silicone rubber composition. The method of claim 1, 10 to 50 ppm by weight of platinum catalyst, based on 100 parts by weight of the composition; And 0.5 to 2 parts by weight of a polymerization inhibitor, wherein the silicone rubber composition comprises: The silicone blanket for micropattern offset printing obtained by heat-hardening or UV-curing the silicone rubber composition of any one of Claims 1-7.

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