JP2009249524A - Curable polyurethane composition for sealing and gasket - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a curable polyurethane composition for sealing from which a cured substance without foaming and swelling and excellent in adhesion is formed. <P>SOLUTION: The curable polyurethane composition for sealing includes each of: (A) a polyether-polyol composed of a polyoxyalkylene triol with a molecular weight of 2,000-8,000; (B) an isocyanate group-containing urethane prepolymer obtained by making a polyoxyalkylene polyol with a molecular weight of 300-4,000 and an isocyanate group-containing compound react with each other; (C) calcium carbonate which is surface treated with an aliphatic acid or with an aliphatic acid ester; and (D) an organic aluminum chelate compound. The gasket is formed by curing such a polyurethane composition. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a curable polyurethane composition for sealing and a gasket, and in particular, has a good sag resistance (slump property), and forms a cured product having excellent adhesion without foaming or swelling. The present invention relates to a polyurethane composition and a gasket obtained by curing the composition.

  In recent years, computer hard disk drives have become more sophisticated and smaller in size, and have a complicated circuit configuration. If a small amount of dust or contaminants enter the magnetic disk, it can cause malfunction. Become. Therefore, it is common practice to use a gasket to prevent dust from entering. For example, a gasket is provided in a seal portion for airtightness and moisture-proofing of a housing and a lid of a hard disk drive case (hereinafter referred to as an HDD case), a small video camera, and portable electronic devices. Such a gasket itself is required not to contain a pollutant and to generate no outgas as a pollutant.

  As a manufacturing method of a gasket for an HDD case, a dispensing method in which a liquid resin such as a two-component polyurethane resin is extruded into a gasket shape by a dispenser and integrated is the mainstream. In this dispensing method, in order to ensure airtightness, it is required that the dispensed resin has no dripping and deformation is small, that is, thixotropy (thixotropy) is good and there is no slump. Yes.

  Conventionally, in order to improve the dripping of the two-component polyurethane resin, as a thixotropic agent, calcium carbonate subjected to a surface treatment with a fatty acid or the like has been blended. This composition has an excess of isocyanate groups and is generally cured by moisture in the air (see, for example, Patent Document 1).

  However, since the method of curing with moisture in the air takes a long time to cure and the productivity is poor, attempts have been made to improve the productivity by heating and curing. Since it reacts with the water and the fatty acid which is the surface treatment agent of calcium carbonate to generate carbon dioxide, there is a problem that foaming and swelling occur in the cured product. And in order to suppress generation | occurrence | production of foaming and a swelling, there existed a problem that adhesiveness fell, when the quantity of the isocyanate group which a polyurethane resin has was reduced.

In addition, it has been proposed to add a silane coupling agent in order to improve adhesion (see, for example, Patent Document 2). However, since siloxane is scattered and easily causes a malfunction of a hard disk, it is used for an HDD case or the like. It was difficult to use for gaskets. Furthermore, proposals have been made to improve adhesion by adding a titanium coupling agent (see, for example, Patent Document 3), but the organic titanium compound itself, which is a titanium coupling agent, also serves as a catalyst for the urethanization reaction. Therefore, there is a problem that foaming and swelling are likely to occur in the cured product, and the pot life is shortened.
JP 2004-231782 A JP 2006-1111811 A JP 2000-219806 A

  The present invention has been made to solve these problems, and has a thixotropic property, no dripping (slump), and is capable of forming a cured product having excellent adhesion without foaming or swelling. It is an object to provide a curable polyurethane composition and a gasket produced from the composition.

  The sealing curable polyurethane composition of the present invention comprises (A) a polyether polyol composed of a polyoxyalkylene triol having a weight average molecular weight (hereinafter referred to as Mw) of 2000 to 8000, and (B) Mw of 300 to 4000. A urethane prepolymer containing an isocyanate group, obtained by reacting a polyoxyalkylene polyol with an isocyanate group, (C) a calcium carbonate surface-treated with a fatty acid or a fatty acid ester, and (D) an organic An aluminum chelate compound is contained, respectively.

  The gasket of the present invention is characterized by curing the curable polyurethane composition for sealing.

  ADVANTAGE OF THE INVENTION According to this invention, the curable polyurethane composition for seals which can form the hardened | cured material which is excellent in thixotropic property, is excellent in slump property, and is excellent in adhesiveness without foaming and swelling can be obtained. Moreover, since this composition can be cured without adding an amine catalyst or an organotin catalyst that may become a contamination source, it is excellent in stain resistance. Therefore, in the gasket formed by curing the curable polyurethane composition for sealing, for example, the sealing property of the HDD case can be improved, and dust can be prevented from entering, and the magnetic disk can be contaminated. Therefore, the occurrence of malfunction due to contamination can be reduced. Therefore, a highly reliable hard disk device can be obtained.

  Hereinafter, embodiments of the present invention will be described.

  The sealing curable polyurethane composition according to the embodiment of the present invention includes (A) a polyether polyol composed of a polyoxyalkylene triol having an Mw of 2000 to 8000, and (B) a polyoxyalkylene polyol having an Mw of 300 to 4000. It contains an isocyanate group-containing urethane prepolymer obtained by reacting an isocyanate group-containing compound, (C) calcium carbonate surface-treated with a fatty acid or fatty acid ester, and (D) an organoaluminum chelate compound.

  In the embodiment of the present invention, the polyether polyol as the component (A) is composed of a polyoxyalkylene triol that is a trifunctional polyether polyol having an Mw of 2000 to 8000.

  The polyoxyalkylene triol as component (A) is a copolymer of polyoxypropylene and other alkylenes such as polyoxyethylene triol, polyoxypropylene triol, and polyoxy (propylene / ethylene) copolymerized triol. Examples include type triols. In particular, it is preferable to use polyoxypropylene triol obtained by ring-opening polymerization of propylene oxide using glycerol or the like as an initiator.

  In the embodiment, Mw of the polyoxyalkylene triol is in the range of 2000 to 8000, more preferably 2500 to 5500. When Mw of the polyoxyalkylene triol is less than 2000, sufficient thixotropy cannot be obtained, and the slump property may be deteriorated. Moreover, when Mw exceeds 8000, the viscosity at the time of kneading | mixing with the surface-treated calcium carbonate of (C) component mentioned later becomes high too much, and workability | operativity falls remarkably.

  In the embodiment of the present invention, the urethane prepolymer as the component (B) is obtained by reacting a polyoxyalkylene polyol having an Mw of 300 to 4000 and a compound containing an isocyanate group, and has an isocyanate group. And a prepolymer containing a urethane bond.

  The polyoxyalkylene polyol used for the preparation of the urethane prepolymer as component (B) is a polyhydric alcohol such as ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, which are divalent alcohols. And polyoxyalkylene triols obtained by ring-opening polymerization of alkylene oxides such as ethylene oxide and propylene oxide, and those having a Mw in the range of 300 to 4000. The use of polyoxypropylene triol is more preferred because it is easy to obtain thixotropic properties and has good slump properties.

  The reason why the Mw of the polyoxyalkylene polyol is limited to the range of 300 to 4000 is that when the Mw is less than 300 or more than 4000, it is difficult to control the curing reaction of the resulting polyurethane composition. Because there is. These polyalkylene polyols can be used alone, or two or more polyoxyalkylene polyols having different Mw (for example, polyoxyalkylene triol) can be used in combination.

  Examples of the compound containing an isocyanate group used for preparing the urethane prepolymer as the component (B) include aromatic isocyanates, aliphatic isocyanates, alicyclic isocyanates, mixtures thereof, and modified organic isocyanate compounds. . Among these, it is preferable to use a polyisocyanate compound having two or more isocyanate groups in the molecule, particularly a polyisocyanate compound having two or more terminal isocyanate groups in the molecule.

  Examples of the compound having an isocyanate group include tolylene diisocyanate (TDI), hydrogenated tolylene diisocyanate, diphenylmethane diisocyanate (MDI), polymeric MDI (PMDI), xylylene diisocyanate (XDI), and 1,5-naphthalene diisocyanate. Fatty acids such as aromatic isocyanates such as (NDI), aliphatic isocyanates such as hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), hydrogenated XDI (H6XDI), hydrogenated MDI (H12MDI), norbornane diisocyanate methyl (NBDI) Examples thereof include cyclic polyisocyanates, carbodiimide-modified isocyanates of the above isocyanates, and isocyanurate-modified products.

  In terms of reactivity, fast-reacting TDI, MDI, carbodiimide-modified MDI (liquid MDI) and PMDI are preferred, and TDI is more preferred. These compounds having an isocyanate group can be used singly or in combination of two or more.

  (B) Although the preparation method of the urethane prepolymer which is a component is not specifically limited, the said polyoxyalkylene polyol and the compound containing isocyanate are mixed by the compounding ratio that a desired isocyanate group content rate (NCO%) is obtained. And it can obtain by making it react for 2 to 4 hours at the temperature of 80-90 degreeC. This reaction is preferably performed in an inert gas atmosphere such as a nitrogen gas atmosphere or an argon gas atmosphere.

  The NCO% of the urethane prepolymer (B) obtained in this way is 1 to 1 so that the reaction control at the time of curing of the obtained polyurethane composition becomes easy and a desired hardness can be obtained as a sealing application. It is preferable to set it as 4 weight%, and the range of 2-3.5 weight% is more preferable.

  The blending amount of the urethane prepolymer which is the component (B) thus obtained is preferably 100 to 180 parts by weight, and 120 to 160 parts per 100 parts by weight of the polyether polyol (polyoxyalkylene triol) which is the component (A). A range of parts by weight is more preferred. (B) When the compounding amount of the urethane prepolymer is less than 100 parts by weight, a good urethane composition may not be obtained, and there is a risk of uncured. When it exceeds 180 parts by weight, the hardness of the cured product is There is a risk that the airtightness may be impaired due to the excessive increase. By using the urethane prepolymer as the component (B) in the above ratio, dripping of the resulting polyurethane composition can be improved.

  The calcium carbonate surface-treated with the fatty acid or fatty acid ester which is the component (C) used in the embodiment is a reinforcing filler.

  As the fatty acid or fatty acid ester which is the surface treatment agent, stearic acid, stearic acid ester, or the like can be used. In addition to the fatty acid, a surface treatment can be performed using a sulfonic acid-based surfactant which is an anionic surfactant. Examples of the sulfonic acid-based surfactants include hexylbenzene sulfonic acid, octylbenzene sulfonic acid, dodecylbenzene sulfonic acid, tetradesense sulfonic acid, hydroxytetradesense sulfonic acid, and sodium and potassium salts thereof. The blending of calcium carbonate surface-treated with such a fatty acid has a great effect of improving the reinforcement.

  Since thixotropy is improved and workability is improved, it is preferable that calcium carbonate surface-treated with the fatty acid (C) as the component (C) is previously mixed with the polyether polyol as the component (A).

  The blending amount of the calcium carbonate surface-treated with the fatty acid or the like as the component (C) is preferably 80 to 180 parts by weight with respect to 100 parts by weight of the polyether polyol as the component (A). A range of parts by weight is more preferred. When the blending amount of the component (C) is less than 80 parts by weight, sufficient thixotropy may not be imparted, and when it exceeds 180 parts by weight, the viscosity may be too high and workability may be deteriorated. is there.

In the embodiment, the organoaluminum chelate compound as the component (D) is a component that imparts adhesiveness to a composition such as aluminum to the composition. Examples of the organoaluminum chelate compound include acetoalkoxyaluminum diisopropylate having the structural formula shown below.

  Since this organoaluminum chelate compound has a very weak action (catalytic activity) as a catalyst for promoting the curing reaction, it is a conventional adhesiveness-imparting agent, and a titanium coupling agent (organotitanium compound that acts as a catalyst for the urethanization reaction) ) Is less likely to foam and swell in the cured product, and has a merit that a sufficient pot life can be realized.

  The compounding amount of the organoaluminum chelate compound as component (D) is preferably 0.5 to 6 parts by weight with respect to 100 parts by weight of the polyether polyol as component (A), and 2 to 4 parts by weight. A range is more preferred. When the blending amount of the component (D) is less than 0.5 parts by weight, the adhesiveness may not be sufficiently provided. When it exceeds 6 parts by weight, it acts as a catalyst for the urethanization reaction, There is a risk of blistering.

  The organoaluminum chelate compound as the component (D) is preferably mixed with the polyether polyol as the component (A) in advance together with the calcium carbonate surface-treated with the fatty acid (C). Then, a two-component type (two-component) that obtains a curable composition by heating and kneading the polyether polyol composition containing component (C) and component (D) and the urethane prepolymer that is component (B). It is preferable to adopt a usage mode of (type). The mixing method is not particularly limited, and the desired method is considered in consideration that the active hydrogen group (hydroxyl group) of the polyol in component (A) reacts with the isocyanate group in (B) urethane prepolymer by subsequent heat curing. Can be taken.

  The curable polyurethane composition for sealing according to the embodiment of the present invention includes a filler, a plasticizer, an anti-aging agent, an ultraviolet absorber, a light stabilizer, an antioxidant, a pigment or dye coloring agent, a dispersant, and the like. An agent can be mix | blended in the range which does not impair the effect of this invention. In addition, these additives can be mix | blended with the polyether polyol which is (A) component, or can be mix | blended with the composition after mixing each component of (A)-(D).

  The sealing curable polyurethane composition according to the embodiment is a catalyst used as necessary in the reaction of the polyether polyol as the component (A) and the urethane prepolymer as the component (B), for example, dibutyltin dilaurate, Organic tin compounds such as dioctyltin dimaleate or amine-based catalysts such as triethylamine, tetraethylenediamine and N-methylmorpholine are not substantially contained. Therefore, the polyurethane composition of the embodiment does not cause bleed-out of a catalyst or the like, and is excellent in contamination resistance. For example, even if a gasket for HDD case is formed, contamination of the hard disk device does not occur. . In order to form a gasket using the curable polyurethane composition of the embodiment, for example, after defoaming the obtained composition, it is dispensed on one side of the housing case of the hard disk to form a desired gasket shape, A method of heating and curing at 50 to 200 ° C., preferably 100 to 160 ° C. for 1 to 10 hours can be employed. In the HDD case gasket thus obtained, the generation of contaminants after assembling the housing case formed with the gasket and the hard disk is suppressed.

  Thus, according to the embodiment of the present invention, it is possible to obtain a curable polyurethane composition excellent in slump property (sag resistance) and stain resistance. Moreover, the cured product obtained from this curable polyurethane composition does not foam or swell and is excellent in adhesiveness. Therefore, in a gasket for HDD cases or the like formed from this curable polyurethane composition, slump (liquid dripping) is suppressed, so that airtightness as a gasket is improved, and dust intrusion can be suppressed. In addition, since the generation of contaminants is suppressed in the gasket obtained by heat-curing this curable polyurethane composition, it is possible to reduce malfunctions due to contamination of contaminants on the magnetic disk, for example. A high hard disk drive can be obtained.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to a following example.

(Preparation Example 1) (Preparation of polyether polyol composition 1)
130 parts by weight of MS2000 (surface-treated calcium carbonate, manufactured by Maruo Calcium Co., Ltd.) was added to and mixed with 100 parts by weight of Exenol 3030 (polyoxypropylene triol with Mw of 3000, manufactured by Asahi Glass Co., Ltd.) as shown below. That is, first, 130 parts by weight of MS2000 was added to 74.3 parts by weight of Exenol 3030, heated and kneaded at 100 ° C. for 4 hours, cooled to room temperature, and then 25.7 parts by weight of Exenol 3030 was added. Mixed.

  Subsequently, 3 parts by weight of preneact AL-M (acetoalkoxyaluminum diisopropylate, manufactured by Ajinomoto Fine Techno Co., Ltd.) was added to and mixed with this mixture to obtain a polyether polyol composition 1.

(Preparation Example 2) (Preparation of polyether polyol composition 2)
After adding 130 parts by weight of MS2000 to 74.3 parts by weight of Exenol 3030, heating and kneading at 100 ° C. for 4 hours, cooling to room temperature, adding 25.7 parts by weight of Exenol 3030 and mixing, A polyether polyol composition 2 was obtained.

(Preparation Example 3) (Preparation of polyether polyol composition 3)
Instead of adding 3 parts by weight of Preneact AL-M, 3 parts by weight of Titacoat S-181 ((2-n-butoxycarbonylbenzoyloxy) tributoxytitanium, manufactured by Nippon Kayoda Co., Ltd.) was added. Otherwise in the same manner as in Preparation Example 1, a polyether polyol composition 3 was obtained.

(Preparation Example 4) (Preparation of urethane prepolymer)
Tolylene diisocyanate (2,4-isomer / 2,6) with respect to a mixture of 92.9 parts by weight of Exenol 3030 and 7.1 parts by weight of Exenol 430 (Mw420 polyoxypropylene triol, manufactured by Asahi Glass Co., Ltd.) -Isomer = 80/20) 19.9 parts by weight were added and reacted at 80 ° C. for 3 hours under a nitrogen stream to obtain a urethane prepolymer having an NCO% of 3.0% by weight.

Example As shown in Table 1, the polyether polyol composition 1 obtained in Preparation Example 1 and the urethane prepolymer obtained in Preparation Example 4 were mixed with 100 parts by weight of Exenol 3030 as shown in Table 1. The mixture was mixed so as to be 140.2 parts by weight with respect to the mixture.

Comparative Example 1
The polyether polyol composition 2 obtained in Preparation Example 2 and the urethane prepolymer obtained in Preparation Example 4 were blended in the proportions shown in Table 1, and mixed in the same manner as in the Examples.

Comparative Example 2
The polyether polyol composition 3 obtained in Preparation Example 3 and the urethane prepolymer obtained in Preparation Example 4 are blended in the proportions shown in Table 1, and heated and mixed using a planetary mixer in the same manner as in the Examples. Kneaded.

  Next, after defoaming each of the polyurethane compositions obtained in Examples and Comparative Examples 1 and 2, it was applied to an aluminum plate, heated at 80 ° C. for 1 hour, and further heated at 140 ° C. for 1 hour to be cured. And the presence or absence of foaming of hardened | cured material was investigated with the naked eye. Further, using aluminum as an adherend, the shear bond strength was measured as follows. That is, one end of two aluminum plates having a width of 25 mm was placed over a length of 10 mm with the composition layer (thickness 1 mm) obtained in Example 1 and Comparative Examples 1 and 2 in between. Then, the composition layer was cured by heating at 80 ° C. for 1 hour and then at 140 ° C. for 1 hour. The shear bond strength was measured by pulling both ends of the test specimen thus produced with a tensile tester. Table 1 shows the measurement results of the presence or absence of foaming and the shear bond strength.

  As can be seen from Table 1, the polyurethane compositions obtained in the examples can form a cured product having no foaming and excellent adhesion to an aluminum plate. On the other hand, the hardened | cured material obtained from the polyurethane composition of the comparative example 1 which is not mix | blending the pre-act AL-M which is an organoaluminum chelate compound has remarkably low adhesive strength with respect to an aluminum plate. Moreover, although the hardened | cured material obtained from the polyurethane composition of the comparative example 2 which mix | blended titacoat S-181 which is a titanium-type silane coupling agent instead of pre-act AL-M, the adhesive strength with respect to an aluminum plate is favorable. , Foaming and swelling are seen with the naked eye, which is not preferable.

  Furthermore, the polyurethane composition obtained in the example was dispensed on one side of a housing case of a hard disk, and heated and cured at 140 ° C. for 3 hours to form a gasket. Then, after assembling the housing case and the hard disk in which the gasket is formed in this way, it is put into a thermostatic bath at 50 ° C. for 7 days, and then the disk is taken out to determine whether or not there is any deposit on the surface with an optical microscope (magnification 100). In each case, no deposit was observed on the surface of the disk, and it was found that the stain resistance was good.

Claims (7)

(A) a polyether polyol composed of a polyoxyalkylene triol having a weight average molecular weight (Mw) of 2000 to 8000,
(B) a urethane prepolymer containing an isocyanate group, obtained by reacting a polyoxyalkylene polyol having a weight average molecular weight (Mw) of 300 to 4000 and a compound containing an isocyanate group;
(C) calcium carbonate surface-treated with a fatty acid or a fatty acid ester;
(D) A curable polyurethane composition for sealing, which contains an organoaluminum chelate compound.   The curable polyurethane composition for sealing according to claim 1, wherein the urethane prepolymer as the component (B) has an isocyanate group content of 1 to 4% by weight.   The curable polyurethane composition for sealing according to claim 1 or 2, wherein the component (C) is calcium carbonate surface-treated with a fatty acid and a sulfonic acid surfactant.   The amount of the surface-treated calcium carbonate as the component (C) is 80 to 180 parts by weight with respect to 100 parts by weight of the polyether polyol as the component (A). 4. The sealing curable polyurethane composition according to any one of 3 above.   The curable polyurethane composition for sealing according to any one of claims 1 to 4, wherein the organoaluminum chelate compound as the component (D) is acetoalkoxyaluminum diisopropylate.   The amount of the organoaluminum chelate compound as the component (D) is 0.5 to 6 parts by weight with respect to 100 parts by weight of the polyether polyol as the component (A). The curable polyurethane composition for seals according to any one of 5.   A gasket obtained by curing the curable polyurethane composition for sealing according to any one of claims 1 to 6.