JP2010235805A - Closed-cell urethane sheet and production method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a closed-cell urethane sheet which has the density lower than before and both of high extensibility and high strength while keeping waterproofness as a sealing material and to provide a production method of the closed-cell urethane sheet. <P>SOLUTION: The closed-cell urethane sheet is obtained by mixing a thermally expandable microcapsule in a liquid urethane raw material and is used as the sealing material. The liquid urethane raw material comprises an isocyanate-terminated urethane prepolymer being a reaction product obtained by reacting dimer acid-based polyol, low molecular weight glycol and isocyanate. The closed-cell urethane sheet has ≥90° contact angle. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a closed-cell urethane sheet and a method for producing the same. Specifically, the present invention relates to a closed-cell urethane sheet used as a waterproof sealing material, for example, in the automobile field, such as a car tail lamp seal part, or in the field of construction or home appliances, and a manufacturing method thereof.

  As is well known, flexible urethane foam is generally open-celled. Moreover, even if an attempt is made to obtain closed-cell urethane foam, there is only a method to withstand the shrinkage force by increasing the rigidity of urethane in order to prevent shrinkage. However, in this method, a hard urethane foam can be obtained, but a soft urethane foam cannot be obtained in principle.

  Conventionally, for example, Patent Documents 1 to 3 are known as techniques related to urethane foam.

Patent Document 1 discloses a technique in which a specific polyol compound, a polyfunctional isocyanate compound, and a foam stabilizer are added and stirred in the presence of a non-reactive gas to obtain a meringue cell dispersion and then cured. ing. Patent document 1 aims at providing the flexible polyurethane foam which is excellent in shock absorption and cushioning properties, and does not have a feeling of bottoming. However, in this technique, since bubbles are mixed by mechanical stirring, the density is as high as 0.85 g / cm ³ as described in Example 1, and cannot be reduced.

Patent Document 2 discloses a method for producing a polyurethane foam obtained by dissolving a gas having a specific solubility in a specific polypropylene glycol. However, in the case of Patent Document 2, the average density of the polyurethane foam is not as low as 0.6 to 1.0 g / cm ³ .

  Patent Document 3 discloses a polyurethane foam composition in which a thermally expandable microcapsule is blended in a polyurethane composition containing a liquid polyurethane prepolymer and water. Patent Document 3 aims at obtaining a urethane foam having low hardness and excellent wear resistance, and a paper sheet transport roll is cited as an application. In Patent Document 3, the amount of thermally expanded microcapsules is as small as 0.25 to 1.0 parts by weight.

JP 2005-264048 A JP 2006-206793 A Japanese Patent Laid-Open No. 6-199978

  The present invention has been made in consideration of such circumstances, and a closed-cell urethane sheet having a low density as compared with the conventional one and maintaining high waterproofness as a sealing material, and having both high elongation and strength, and a method for producing the same. The purpose is to provide.

  The closed-cell urethane sheet according to the present invention is a closed-cell urethane sheet used as a sealing material, in which thermally expanded microcapsules are blended with a liquid urethane material, and the liquid urethane material is a dimer acid-based polyol and a low molecular weight glycol. And an isocyanate-terminated urethane prepolymer which is a reaction product of isocyanate and the contact angle of closed-cell urethane is 90 degrees or more.

  The process for producing a self-foaming urethane sheet according to the present invention comprises a liquid urethane raw material comprising a dimer acid-based polyol and an isocyanate-terminated urethane prepolymer which is a reaction product of a low molecular weight glycol and an isocyanate, and a thermal expansion microcapsule. A step of applying a urethane raw material containing the thermal expansion microcapsule in a sheet form on at least one side of the releasable substrate, and foaming and curing the sheet-like liquid urethane raw material to form a urethane sheet. It is characterized by comprising the step of forming.

  According to the present invention, a closed-cell urethane sheet having high elongation and strength that is practically satisfactory as a sealing material can be obtained. Moreover, according to the obtained self-foaming urethane sheet, moisture permeability can be significantly reduced along with high water-stopping properties.

FIG. 1: shows sectional drawing which shows a manufacturing method in order of a process about an example of the closed cell urethane sheet which concerns on this invention. FIG. 2 shows a cross-sectional view of a closed cell urethane sheet having a skin layer on one side according to the present invention.

Next, the present invention will be described in more detail.
As is well known, a flexible urethane foam is generally open-celled, but a urethane foam that exhibits water-stopping properties can be made by using a hydrophobic raw material. This is disclosed in, for example, Japanese Patent Publication No. 59-37036 and Japanese Patent Publication No. 58-17784. However, water vapor permeates due to open cells, and condensation may occur near the seal structure depending on conditions. Therefore, a closed cell type water-proof sealing material is desired for applications in which dew condensation causes trouble.

  In order to realize a closed-cell type urethane sealant, the present inventors have been researching foamed urethane foams in which expanded microcapsules are blended with urethane raw materials, and as a result, simply expanded microcapsules and liquid urethane raw materials. It is difficult to obtain sufficient elongation and strength with only the blending, and it has already been found that there is a practical problem that it is torn or cut at the time of adhesion when used as a sealing material.

  For this reason, as described above, the present inventor blended thermal expansion microcapsules with a liquid urethane raw material, and the liquid urethane raw material is a reaction product of dimer acid polyol, low molecular weight glycol and isocyanate. The present invention has led to the investigation of a closed-cell urethane sheet comprising a certain isocyanate-terminated urethane prepolymer and having a closed-cell urethane contact angle of 90 degrees or more. In the present invention, when the thermally expanded microcapsules are blended and at the same time a hydrophobic urethane having a contact angle of 90 degrees or more is added, closed cells are added, so that the water-stopping property and moisture permeability resistance are greatly improved.

In this invention, a liquid urethane raw material consists of a dimer acid type polyol, said isocyanate terminal prepolymer, a foaming agent, a catalyst, a crosslinking agent, etc., A urethane foam can be manufactured by mixing these.
Examples of the polyol that can be used include dimer acid polyester polyol. Dimer acid is a dimer of unsaturated fatty acid such as tall oil fatty acid, which is a substantially divalent fatty acid. The dimer acid polyester polyol is a polyester of this dimer acid and a short chain diol. Other dimer acid polyols include dimer diols obtained by hydrogenation of dimer acid and polyesters of dibasic acids such as adipic acid and sebacic acid, or propylene oxide and ethylene oxide added to dimer acid and dimer diol. Examples include polymerized alkylene polyols. By using these dimer acid-based polyols, hydrophobicity is improved, and water-stopping and moisture permeability are improved.

  In the present invention, an isocyanate-terminated prepolymer which is a reaction product of a low molecular weight glycol and an isocyanate is a low molecular weight glycol such as polyalkylene glycol, polyester diol, polytetramethylene glycol, polycaprolactone glycol or the like and an MDI-based polypolymer. It is a reactive organism with diisocyanates such as aromatic polyisocyanates such as isocyanate, tolylene diisocyanate, tolidine diisocyanate and naphthalene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate and hydrogenated XDI. The molecular weight of the low-molecular glycol is preferably from 300 to 1,000 because it is remarkable that the elongation and strength are improved. The NCO% of these isocyanate-terminated prepolymers is preferably 10 to 25% because elongation / strength is improved and the viscosity of the raw material is low.

  In the present invention, it is desirable that the mixing ratio of the isocyanate-terminated prepolymer and the polyol is such that NCO / OH (index) is in the range of 0.8 to 1.4. Here, when the index is less than 0.8, properties such as water-stopping property or permanent distortion of the obtained polyurethane foam are lowered, and when it exceeds 1.4, the crosslinking reaction is excessively advanced and the moldability is lowered.

In the present invention, additives such as a catalyst, a crosslinking agent, a foam stabilizer, a chain extender, and a viscosity reducing agent can be appropriately blended as in the conventional production method.
In the present invention, a known amine catalyst or organometallic catalyst can be used as the catalyst. Specifically, for example, bis (dimethylaminoethyl) ether, pentamethyldiethylenetriamine, N, N-dimethylcyclohexylamine, N, N-dimethylethanolamine, N, N, N ′, N′-tetramethylhexamethylenediamine, N, N, N ′, N′-tetramethylpropylenediamine, N, N, N ′, N′-tetramethylethylenediamine, triethylenediamine, N-methyl-N ′-(dimethylamino) ethylpiperazine, N-methylmono Forin, N-ethylmonoforin, triethylamine, tin laurate, and tin octoate are mentioned. The amount of the catalyst added is generally preferably about 0.01 to 5 parts by weight with respect to 100 parts by weight of the polyol component.

  In the present invention, a crosslinking agent having a relatively low molecular weight is used. For example, diol, triol, polyvalent amine, those obtained by adding ethylene oxide or propylene oxide, triethanolamine, diethanolamine, or the like can be used. The addition amount of the crosslinking agent is generally preferably about 0 to 20 parts by weight with respect to 100 parts by weight of the polyol component. As the foam stabilizer, a commonly used silicone foam stabilizer can be used as appropriate. In addition, according to the performance requested | required of a polyurethane foam, a flame retardant, a filler, an antistatic agent, a coloring agent, a stabilizer, etc. can be added in the range which does not deviate from the objective of this invention as needed.

  In the present invention, as a method of making the urethane foam contact angle 90 ° or more, that is, a hydrophobic urethane, for example, as hydrophobic oil addition, hydrophobicity such as asphalt, tackifying resin, petroleum resin, polybutene, wax, etc. A method for adding a water-resistant waterproofing material, a method using a hydrophobic polyol mainly composed of carbon and hydrogen, such as an olefinic polyol, a polybutadiene-based polyol, a dimer acid-based polyol, or a castor oil-based polyol as a hydrophobic polyol, As a foam stabilizer, a method using a silicone compound having a functional group that reacts with an isocyanate such as OH group or amino group in the molecule, a silicone oil having no functional group, or a fluorine foam stabilizer, or diphenylmethane diisocyanate as an isocyanate. Has many aromatic rings such as isocyanate Such as a method of using an isocyanate in large quantities, and the like.

In the present invention, the thermally expandable microcapsule is a liquid or gas that expands when heated.For example, propane, butane, normal butane, isobutane, isopentane, normal pentane, hexane, methylene chloride, chlorofluorocarbons, etc. are used as synthetic resin capsules. It is included. The kind of synthetic resin is a copolymer such as acrylonitrile, acrylic acid ester, methacrylic acid ester, styrene, vinyl acetate, and vinylidene chloride. In addition, styrene beads, polypropylene beads, polyethylene beads and the like in which carbon dioxide gas is impregnated with styrene resin known as foam beads are also suitable as the expandable microcapsules.
The auxiliary foaming agent is a foaming agent used in the production of ordinary urethane foam. When used in combination with volatile organic compounds such as water, low-boiling hydrocarbons, fluorine-based compounds, and chlorine-based compounds, the low-density foam is stabilized. Is preferable.

In the present invention, as a method of applying a liquid urethane raw material containing thermally expandable microcapsules in a sheet form on at least one side of a releasable substrate, a silicone resin is applied to the surface of paper or polyester film as a releasable substrate. Or a resin film such as polypropylene or polymethylpentene, which itself has releasability, is applied by a coating method.
As a method of applying the liquid urethane raw material, for example, a roll coater, a knife coater, a die coater, or a spray coater can be cited as a suitable means.

  In the present invention, the closed-cell urethane sheet is produced, for example, as shown in FIGS.

First, a polyol, isocyanate, a catalyst, a thermally expandable microcapsule, and other additives are mixed to prepare a liquid urethane raw material. Next, as shown to FIG. 1 (A), the liquid urethane raw material 2 is apply | coated uniformly on the 1st film 1a as a mold release base material. Subsequently, the second film 1b is placed on the liquid urethane raw material 2 (see FIG. 1B). Further, the liquid urethane raw material sandwiched between the first and second films 1a and 1b is placed in an oven and heated uniformly at 60 ° C to 130 ° C. Thereby, foaming and resinification progress and the closed-cell urethane sheet 3 is formed. If the heat-expandable microcapsules are not uniformly heated, the expansion ratio is not uniform and the thickness and other dimensions are not constant, and thus a well-formed sheet-like urethane foam cannot be obtained. Next, after taking out the closed cell urethane sheet 3 sandwiched between the first and second films 1a and 1b, the first and second films 1a and 1b are peeled off to form the skin layers 4 on the upper and lower surfaces. A finished product is obtained (see FIG. 1C).
In addition, in FIG. 1, although the case where the 1st, 2nd films 1a and 1b were peeled was described, it is not restricted to this, As shown in FIG. 2, only the 2nd film 1b is peeled and the 1st film 1a May be left. In this case, the closed cell urethane sheet 3 having the skin layer 4 on one side is integrated with the first film 1a. Moreover, although this invention is not shown in figure, this invention also extends to the closed-cell urethane sheet which has the 1st and 2nd film on both surfaces.

  In the present invention, as a means for foaming the sheet-like liquid urethane raw material by heating, a urethane stock solution containing thermally expandable microcapsules is applied onto a releasable substrate, and then introduced into a heating device at 60 ° C. Heating to ~ 130 ° C can be mentioned. Thereby, expansion | swelling of a microcapsule progresses simultaneously with hardening of urethane. When the auxiliary foaming agent is used, foaming by the auxiliary foaming agent proceeds simultaneously with heating, and the expansion of the microcapsules proceeds with a slight delay.

Hereinafter, specific examples of the present invention will be described. Note that the present embodiment is not limited to the following description. In the text, “part” is based on mass.
Example 1
First, dimer acid polyester polyol (manufactured by DIC, 100 parts of a polyester polyol composed of dimer acid having a molecular weight of 1300 and a hydroxyl value of 120 and diethylene glycol), 0.9 part of water, a silicone foam stabilizer (trade name: NP manufactured by Shin-Etsu Chemical Co., Ltd.) -405) Liquid urethane raw material consisting of 1 part, 0.3 part of stanoct SO (tin-based catalyst), 112 parts of isocyanate-terminated prepolymer (DC5600 made by Nippon Polyurethane, prepolymer consisting of polypropylene glycol and MDI having a molecular weight of 600) , 10 parts of expanded microcapsules (trade name: Expancel DU40, expanded microcapsules manufactured by Nippon Philite Co., Ltd.) were mixed and stirred at a liquid temperature of 35 ° C. Next, the liquid urethane raw material blended with the microcapsules was coated using a knife coater provided with a 1.8 mm gap on a polyester release film. Next, after heating at 70 ° C. for 3.5 minutes in a heating oven and then heating at 130 ° C. for 6.5 minutes, the sheet-like urethane product was peeled from the release film. The obtained product had a contact angle of 95 degrees, a density of 0.0955 g / cm ³ , a closed cell ratio of 13% and a thickness of about 10 mm and a very smooth surface. In addition, the tensile strength was 196 kPa, the elongation was 120%, the moisture permeability was 1.3 g, and the water stopping property was 160 mm.

(Example 2)
A sheet-like urethane was prepared in the same manner as in Example 1 except that the dimer acid polyester polyol in Example 1 was changed to a hydroxyl value of 80 and the isocyanate-terminated prepolymer was changed to 81.7 parts. The obtained product had a contact angle of 95 degrees, a density of 0.0925 g / cm ³ , a closed cell ratio of 15%, and a very smooth surface having a thickness of about 10 mm. Further, the tensile strength was 181 kPa, the elongation was 140%, the moisture permeability was 1.3 g, and the waterstop was 160 mm.

(Comparative Example 1)
First, 100 parts of Exenol 4600 (trade name manufactured by Asahi Glass Co., Ltd., polypropylene glycol having a molecular weight of 5000 and a hydroxyl value of 34.5), 15 parts of FTR 1600 (petroleum resin under the trade name of Mitsui Chemicals), 2.0 parts of water, NP -405 (silicone foam stabilizer under the trade name of Shin-Etsu Chemical Co., Ltd.), 0.3 part of stanoct SO (tin-based catalyst), T65 (toluene diisocyanate under the trade name of Nippon Polyurethane) 25.9 parts The liquid raw material was stirred at a liquid temperature of 35 ° C. Next, this liquid urethane raw material was coated on a polyester release film using a knife coater having a gap of 1.8 mm. Subsequently, after heating in a heating oven at 70 ° C. for 3.5 minutes and further at 130 ° C. for 6.5 minutes, the closed cell urethane sheet (sheet-like urethane product) was peeled from the release film. The obtained product had a contact angle of 95 degrees, a density of 0.094 g / cm ³ , a closed cell rate of 0%, and a thickness of about 10 mm and a very smooth surface. The tensile strength was 113 kPa, the elongation was 120%, the moisture permeability was 4.5 g, and the water stoppage was 70 mm.

(Comparative Example 2)
First, Teslac 2456 (trade name, manufactured by Hitachi Chemical Polyol Co., Ltd., molecular weight 1000, hydroxyl value 130, polyester polyol composed of dimer acid and diethylene glycol) 100 parts, water 1.6 parts, NP-405 (product manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part of silicone foam stabilizer), 0.2 part of DABCO-33LV (Amine catalyst under the trade name made by Nippon Emulsifier Co., Ltd.), 0.26 part of stannoc SO (tin catalyst), isocyanate-terminated prepolymer (as described above) A liquid urethane raw material consisting of 60.2 parts of NCO% = 30) consisting of dimer acid polyol and T65 was stirred at a liquid temperature of 35 ° C. Next, this liquid urethane raw material was coated on a polyester release film using a knife coater having a gap of 1.8 mm. Subsequently, after heating in a heating oven at 70 ° C. for 3.5 minutes and further at 130 ° C. for 6.5 minutes, the sheet-like urethane product was peeled from the release film. The obtained product had a contact angle of 98 degrees, a density of 0.091 g / cm ³ , a closed cell ratio of 0%, and a thickness of about 10 mm and a very smooth surface. The tensile strength was 147 kPa, the elongation was 110%, the moisture permeability was 3.4 g, and the waterstop was 70 mm.

Next, a method for measuring physical properties will be described.
1) The contact angle was measured by sandwiching the obtained urethane foam with aluminum foil, pressing it at a pressure of about 50 kg / cm ² while heating at about 200 ° C. to form a thin film, and measuring with a Kyowa contact angle measuring machine. .
2) The closed cell rate was measured by ASTM D2856-70 using a test size of a sample size (25 mm × 25 mm × 10 mm) with a Beckman air comparison hydrometer made by Tokyo Science.

3) For the moisture permeability, a test piece of sample size (outer diameter φ75 mm, inner diameter φ35.5 mm, thickness 10 mm) was set in a standard bottle with 50% compression, and about 45 g of silica gel was accurately weighed in the bottle. The weight increase after standing in a high temperature and humidity chamber at 85 ° C. and humidity of 85% for 24 hours.
4) Water-stopping is performed by squeezing a test piece of sample size (outer diameter φ 60 mm, inner diameter 60 mm, thickness 10 mm) onto an acrylic plate with 50% compression and injecting water to observe leakage. The water pressure is increased by 10 mm every 24 hours and the leaked water pressure is regarded as water-stopping.

In Table 1 below, Examples 1 and 2 and Comparative Examples 1 and 2 show the microcapsules, the blending amount of water, and the physical properties of the obtained products.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

  DESCRIPTION OF SYMBOLS 1a ... 1st film (mold release base material), 1b ... 2nd film (mold release base material), 2 ... Liquid urethane raw material, 3 ... Self-foaming urethane sheet, 4 ... Skin layer.

Claims (2)

It is a closed-cell urethane sheet used as a sealing material, which is made by blending thermally expanded microcapsules with a liquid urethane material.
The liquid foam raw material is composed of an isocyanate-terminated urethane prepolymer which is a reaction product of a dimer acid polyol and a low molecular weight glycol and an isocyanate, and the contact angle of the closed cell urethane is 90 degrees or more. Urethane sheet. Liquid urethane raw material composed of isocyanate-terminated urethane prepolymer which is a reaction product of dimer acid polyol and low molecular weight glycol and isocyanate, a step of blending thermal expansion microcapsules, and a urethane raw material blending these thermal expansion microcapsules And a step of applying a sheet on at least one side of the releasable substrate and a step of foaming and curing the sheet-like liquid urethane raw material by heating to form a urethane sheet. A method for producing a urethane sheet.

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