JP5201346B2 - Polyester polyol and polyurethane elastomer - Google Patents

Description

  The present invention relates to polyester polyols and polyurethane elastomers. Specifically, the present invention relates to a specific polyester polyol useful as a raw material for a polyurethane elastomer excellent in solvent resistance and water resistance, and a polyurethane elastomer using the polyester polyol.

  Polyurethane elastomer is a material obtained by reacting polyol and polyisocyanate together with a crosslinking agent. It has excellent mechanical strength, wear resistance, low-temperature properties, etc., and has a wide range of hardness and elasticity. It is used as a component of various industrial equipment such as pavement materials, adhesives, sealants, and rollers.

  Polyurethane elastomers are classified according to the polyol component used, and include polyether-based, polyester-based, polycaprolactone-based, polycarbonate-based and the like. These polyols include polytetramethylene ether glycol (PTMG) for polyethers, 1,4-butanediol adipate for polyesters, and polycaprolactone for polylactones having a number average molecular weight of about 500 to 5000. The physical properties of polyurethane elastomers depend largely on the composition and structural characteristics of the polyol, and are used in various applications depending on the physical properties. For example, polyurethane elastomers using succinic polyester polyols are widely used as polyurethane rollers for printing presses because of their excellent solvent resistance (Patent Document 1).

  In recent years, water-based inks are being used in place of oil-based inks from the viewpoint of environmental hygiene. However, although polyurethane elastomers using succinic polyester polyols are excellent in solvent resistance, they are inferior in water resistance and hydrolysis resistance, and therefore cannot be used for a long time in applications using aqueous ink. In addition, water-based inks that are currently widely used include water-soluble solvents such as glycol ethers, and polyurethane rollers for printing presses are required to have water resistance and solvent resistance even for water-based inks. Thus, a polyurethane elastomer having both solvent resistance and water resistance is required.

  Other than the polyurethane elastomer using succinic polyester polyol, a polyurethane elastomer using a polycarbonate polyol can be cited as an excellent solvent resistance (Patent Document 2). This is excellent in solvent resistance, water resistance, and alkali resistance, and can be used in applications such as those using the above water-based ink. However, since polycarbonate polyol is generally expensive, it is difficult to use it as a general-purpose product or a consumable product, and it has a drawback that it is solid at room temperature or has a very high viscosity.

On the other hand, in the field of rigid urethane foams, especially by reacting with aromatic polybasic acids, alcohol components and fatty acids having 8 to 30 carbon atoms or oils or fatty acid compounds containing them as components, low viscosity and melting of CFCs A polyester polyol composition having high properties has been proposed (Patent Document 3). However, the polyurethane elastomer using this material and its influence on water resistance have not been studied.
JP-A-5-301335 JP 2004-217844 A Japanese Patent No. 3197508

  Therefore, an object of the present invention is to provide a specific polyester polyol useful as a raw material for a polyurethane elastomer excellent in solvent resistance and water resistance, which can be used at low cost and for general purposes, and a polyurethane elastomer using the polyester polyol. There is.

  As a result of intensive studies by the inventors to achieve these objects, the inventors have obtained knowledge that the above problems can be solved by using a polyester polyol having a specific structural characteristic as a raw material for a polyurethane elastomer. It came to be completed. That is, by using succinic acid and / or adipic acid as a carboxylic acid component, and a polyester polyol using a mono- or polyoxyalkylene glycol having a number average molecular weight of 400 or less as an alcohol component, further using castor oil, the solvent resistance is improved. It was found that water resistance can be imparted while maintaining the above, and the present invention has been completed.

That is, this invention has the summary characterized by the following.
(1) Polyester polyol for polyurethane elastomer, using succinic acid as a carboxylic acid component, and mono or polyoxyalkylene glycol having a number average molecular weight of 400 or less as an alcohol component, and dehydrating and condensing these together with castor oil In the obtained polyester polyol, the hydroxyl value of the polyester polyol is 20 to 200 mg KOH / g, and the amount of castor oil used is 10 to 60% by weight with respect to the obtained polyester polyol.
(2) The polyester polyol according to (1), wherein the mono- or polyoxyalkylene glycol having a number average molecular weight of 400 or less is diethylene glycol and / or triethylene glycol.
(3) A polyurethane elastomer obtained by reacting at least a polyisocyanate, a polyol and a crosslinking agent, wherein the polyester polyol according to (1) or (2) is used as at least a part of the polyol. .

  According to the present invention, a polyester polyol for polyurethane elastomer having excellent solvent resistance and water resistance can be provided. The polyester polyol of the present invention can also be used in the fields of paints, adhesives, plasticizers and the like as a material excellent in water resistance.

  Hereinafter, the present invention will be described in detail. The polyester polyol of the present invention is obtained by using succinic acid and / or adipic acid as the carboxylic acid component, mono- or polyoxyalkylene glycol having a number average molecular weight of 400 or less as the alcohol component, and dehydrating condensation of castor oil together with these. Polyester polyol.

In the present invention, succinic acid and / or adipic acid is used as the carboxylic acid component constituting the polyester polyol. Other carboxylic acids that can be used in combination include acetic acid, oxalic acid, malonic acid, glutaric acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, fumaric acid, maleic acid, malic acid, citric acid, hexahydrophthalic acid And aromatic carboxylic acids such as aliphatic or alicyclic carboxylic acids such as benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, and pyromellitic acid.
From the viewpoint of improving solvent resistance, succinic acid and / or adipic acid is used in an amount of 50 mol% or more, preferably 60 mol% or more as the main component of the carboxylic acid component. In particular, the total amount of the carboxylic acid component is preferably succinic acid and / or adipic acid, and the total amount of the carboxylic acid component is most preferably succinic acid. Each carboxylic acid may use an ester derivative such as an anhydride or a methyl ester.

In the present invention, mono- or polyoxyalkylene glycol having a number average molecular weight of 400 or less is used as the alcohol component constituting the polyester polyol. Specific examples include diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, dibutylene glycol, polybutylene glycol and the like. These may be used alone or in combination of two or more, or a mixture of various molecular weights such as commercially available polyethylene glycol 400 may be used. When the number average molecular weight of the polyoxyalkylene glycol exceeds 400, the content of the carboxylic acid unit constituting the polyester polyol is reduced, which leads to a decrease in physical properties.

  In addition to these, alcohol components that can be used in combination include 1,3-butanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, 3-methyl-1,5- Pentanediol, 1,6-hexanediol, neopentyl glycol, cyclohexanediol, cyclohexanedimethanol, butanol, hexanol, octanol, 2-ethylhexanol, nonanol, isononanol, glycerin, trimethylolpropane, diglycerin, pentaerythritol, erythritol, Aliphatic or alicyclic alcohols such as sorbitol, sucrose, benzyl alcohol, aromatic alcohols such as 2-phenoxyethanol, phenols such as phenol, polyethylene glycol, poly Propylene glycol, polyoxyethylene / oxypropylene copolymer polyol, long-chain polyols such as polytetramethylene ether glycol, and the like. From the viewpoint of improving solvent resistance, mono- or polyoxyalkylene glycol having an average molecular weight of 400 or less is used in an amount of 50 mol% or more, preferably 60 mol% or more as the main component of the alcohol component. In particular, it is most preferable that the total amount of the alcohol component is diethylene glycol and / or triethylene glycol.

  The usage-amount of the castor oil used by this invention is 10 to 60 weight% with respect to the polyester polyol obtained. When the amount of castor oil used is 10% by weight or less, the effect of improving the water resistance of the polyurethane elastomer is small. On the other hand, when it exceeds 60% by weight, the solvent resistance of the polyurethane elastomer is deteriorated and the mechanical strength is decreased. Absent. The amount of castor oil used is preferably 15 to 55% by weight, more preferably 20 to 50% by weight, based on the polyester polyol obtained.

  The hydroxyl value of the polyester polyol of the present invention is in the range of 20 to 200 mgKOH / g, preferably 25 to 190 mgKOH / g, and more preferably 30 to 180 mgKOH / g. If the hydroxyl value is less than 20 mgKOH / g, synthesis may be difficult, and the viscosity may increase and handling may be difficult. On the other hand, if it exceeds 200 mgKOH / g, a molecular weight distribution with a large amount of unreacted alcohol component will result. This is not preferred because there is a risk of lowering the physical properties such as flexibility and brittleness of the elastomer.

  The average functional group number of the polyester polyol of the present invention is usually in the range of 1.5 to 4.0. Preferably it is the range of 1.8-3.5. If the average number of functional groups is less than 1.5, the mechanical strength of the resulting polyurethane elastomer may be lowered. On the other hand, when it is larger than 3.5, the viscosity of the polyester polyol is increased, which may make it difficult to handle. The average number of functional groups can be calculated from the charged molar ratio of the raw materials. For convenience, the average number of functional groups of castor oil was calculated as 3.0 in the present invention.

  In the synthesis of the polyester polyol of the present invention, an esterification catalyst is usually used. In general, an acid catalyst is often used as the esterification catalyst. Examples of Lewis acids include orthotitanates such as tetraisopropyl titanate and tetra-n-butyl titanate, and tin compounds such as diethyl tin oxide and dibutyl tin oxide. And metal compounds such as zinc oxide are used. In addition to a Lewis acid, a Bronsted acid such as p-toluenesulfonic acid can also be used.

  It is desirable that the catalyst used for the synthesis of the polyester polyol of the present invention does not affect the reaction behavior of the urethanization reaction. Therefore, among the above esterification catalysts, orthotitanate is preferable, and the amount used is usually 0.1% by weight or less, preferably 0.05%, based on the total of the carboxylic acid component and alcohol component used in the raw material. It is usually 0.001% by weight or more, preferably 0.003% by weight or less in terms of% by weight or less. In some cases, the reaction may be carried out without using these esterification catalysts, and a deactivation treatment may be performed after the reaction, or it may be removed by purification or the like.

  For production of the polyester polyol of the present invention, a general polyester polyol production apparatus and reaction method can be applied. The end point of the reaction is usually determined by the amount of unreacted carboxyl groups of the carboxylic acid component used. If an acid content is present in the polyurethane elastomer, the hydrolysis resistance may decrease. Therefore, it is preferable that the amount of unreacted carboxyl groups, that is, the acid value of the polyester polyol is as low as possible. Therefore, the acid value of the polyester polyol of the present invention is usually 3 mgKOH / g or less, preferably 2 mgKOH / g or less, more preferably 1 mgKOH / g or less. Although there is no particular lower limit, it is 0.1 mgKOH / g based on the reaction conditions and reaction time.

  Examples of a general method for producing a polyurethane elastomer include a one-shot method and a prepolymer method. The one-shot method is a method of obtaining a polyurethane elastomer by simultaneously reacting a polyisocyanate component, a polyol component and, if necessary, a cross-linking agent and other auxiliary agents, and the prepolymer method is a polyisocyanate component, a polyol component and other if necessary In this method, an auxiliary agent is reacted to produce an isocyanate prepolymer, and then a crosslinking agent and other auxiliary agent are further reacted as required to obtain a high molecular weight polyurethane elastomer. As a method for producing the polyurethane elastomer of the present invention, a prepolymer method is preferred for the purpose of producing a polyurethane elastomer having stable physical properties.

   The polyisocyanate is not particularly limited as long as it is an organic compound having two or more isocyanate groups in one molecule. For example, aliphatic such as hexamethylene diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, alicyclic isocyanate such as hydrogenated tolylene diisocyanate and xylylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, polyphenylene polymethylene polyisocyanate, etc. Aromatic polyisocyanate, or a modified product thereof. Furthermore, carbodiimide modified products and urethane modified products of these polyisocyanates are also included. Preferred polyisocyanates are diphenylmethane diisocyanate and hexamethylene diisocyanate.

  As the polyol, at least the above-described polyester polyol of the present invention is used. Further, the polyols that can be used in combination include polyether polyols such as polypropylene glycol (PPG) and polytetramethylene ether glycol (PTMG), polyester polyols such as adipic acid esters, polylactone polyols such as polycaprolactone, and polycarbonate polyols. A polyol etc. are mentioned. Those having a number average molecular weight of about 500 to 5,000 can be suitably used. When used in combination with the polyester polyol of the present invention, the amount of other polyols is desirably 50% by weight or less of the proportion of the total polyol, and most desirably the total amount is the polyester polyol of the present invention.

  Examples of the crosslinking agent include compounds having two or more active hydrogens in one molecule such as alcohols such as ethylene glycol, diethylene glycol, 1,4-butanediol, propylene glycol and glycerin, and alkanolamines such as diethanolamine and triethanolamine. Used. Preferred examples of the crosslinking agent include ethylene glycol and 1,4-butanediol.

   In the polyurethane elastomer of the present invention, other auxiliary agents are used as necessary. Other uses of auxiliary agents are mainly catalysts for promoting or slowing urethanization reaction, reactivity modifiers, plasticizers, fillers, antioxidants, defoamers for adjusting the properties of polyurethane elastomers. , Surfactants and the like. These additives and auxiliaries are not particularly limited, and are used for the purpose of improving physical properties and operability in ordinary polyurethane elastomers, and are used within the range where the effects of the present invention can be obtained. May be.

   EXAMPLES Specific examples of the present invention will be described below in more detail with reference to examples. However, the present invention is not limited to these examples unless it exceeds the gist.

<Synthesis of polyol>
“Polyols 1 to 5” were synthesized using the carboxylic acids and alcohols shown in Table 1 in accordance with known polyester polyol synthesis methods. Moreover, castor oil (a special grade reagent manufactured by Wako Pure Chemical Industries, Ltd.) was used as “polyol-6”. In the table, diethylene glycol is abbreviated as “DEG” and triethylene glycol is abbreviated as “TEG”. The amounts of the carboxylic acid component and the alcohol component were set to the composition ratios for the polyester polyol having the acid value and the hydroxyl value described in Table 1.

The acid value, hydroxyl value and viscosity of “Polyol-1 to 5” were measured by the following methods, and the results are shown in Table 1.
(1) Acid value: measured in accordance with JIS K1557 ₁₉₇₀ .
(2) Hydroxyl value: Measured according to JIS K1557 ₁₉₇₀ .
(3) Viscosity: Measured according to JIS K1557 ₁₉₇₀ . (25 ° C)
(4) Average functional group number: Calculated from the charged composition ratio. The average number of functional groups of castor oil was set to 3.0.
(5) Number average molecular weight: determined in accordance with JIS K1601 ₁₉₈₂ .

<Synthesis of isocyanate prepolymer>
The following raw materials and reactivity modifiers were used for the synthesis of the isocyanate prepolymer.
(1) Polyol-1-6: The above polyol (2) Polyisocyanate: Diphenylmethane diisocyanate ("Millionate MT" manufactured by Nippon Polyurethane Industry Co., Ltd.)
(3) Reactivity regulator: Phosphate ester (“JP-508” manufactured by Johoku Chemical Co., Ltd.)

Isocyanate prepolymers “Prepolymer-1 to 6” were synthesized according to the following method using the above-mentioned raw materials and reactivity control agents. The polyol / polyisocyanate molar ratio was 1/3.

<Synthesis Method of Isocyanate Prepolymer>
A glass reactor equipped with a stirrer, thermometer, pressure gauge, oil bath, etc. and having a volume of 1 liter is charged with polyol, polyisocyanate, and reactivity modifier according to the mixing ratio shown in Table 2, Was defoamed under reduced pressure. Thereafter, the space of the reactor was replaced with nitrogen gas, and then the reactor was started to be heated at normal pressure. The reaction was started when the internal temperature reached 80 ° C., and the reaction was carried out for 2 hours while depressurizing the system and degassing every 30 minutes from the start of the reaction. The isocyanate prepolymer obtained here was shown in Table 2 as "Prepolymer-1 to 6".

The% NCO (terminal isocyanate group concentration) of the isocyanate prepolymer was measured according to JIS K1556 ₁₉₆₈ using dimethylformamide as a solvent, and the results are shown in Table 2.

<Synthesis of polyurethane elastomer>
The following prepolymer and crosslinking agent were used for the synthesis of the polyurethane elastomer.
(1) Prepolymer: Prepolymer-1 to 6
(2) Crosslinking agent: 1,4-butanediol (special grade reagent manufactured by Wako Pure Chemical Industries, Ltd.)

A polyurethane elastomer sheet was molded by the following molding method.

<Molding method>
A predetermined amount of prepolymer preheated to 80 ° C. was weighed into a SUS reactor, and after a predetermined amount of a crosslinking agent was added by a syringe, it was immediately set in a vacuum stirrer and stirred for 30 seconds while degassing under reduced pressure. . Thereafter, the preheated prepolymer was poured into a molding die of a 2 mm thick sheet that had been preheated to 80 ° C., and was heated and cured in a 120 ° C. oven overnight. Thereafter, the polyurethane elastomer sheet was demolded and stored in the room for 2 days or longer, and then the properties of the polyurethane elastomer sheet were evaluated. The blending ratio of the prepolymer and the crosslinking agent was 1.05 in terms of isocyanate index (NCO group / OH group molar ratio).

The following materials were used as the mold and release agent for polyurethane elastomer sheet molding.
(1) Die: Aluminum Internal dimensions 200mm x 200mm x 2mm
(2) Release agent: Fluorine-based release agent spray ("Daifree GA-6010" manufactured by Daikin Industries, Ltd.)

<Evaluation method>
The evaluation test of the obtained polyurethane elastomer was carried out by the following method. The mechanical strength of the polyurethane elastomer was shown in Table 3, and the evaluation results of water resistance and solvent resistance were shown in Tables 4-7.

(1) the mechanical strength of the mechanical strength test polyurethane elastomer was measured in accordance with JIS A7311 _1995, the hardness of the polyurethane elastomer has been described and the results measured in accordance with JIS K711 ₁₉₉₅ Table 3. The following tensile test pieces and tear test pieces are used, and the moduli of 100%, 200%, and 300% are abbreviated as 100% M, 200% M, and 300% M, respectively, in the table. did.
Tensile test piece: JIS K7113 No. 2 Tear test piece: JIS K7311 No. 3

(2) Water resistance test After a test piece for mechanical strength measurement was immersed in water (60 ° C) for 1 week, the change in the weight of the test piece and the change in the test result by the mechanical strength test in (1) above were measured. The change in weight before and after immersion of the test piece (an index of the amount of swelling) and how much the original mechanical strength was lost was used as the evaluation result of water resistance. The evaluation results are based on the weight of the specimen before immersion and the mechanical strength test values (breaking strength, elongation at break, 100% modulus, 200% modulus, 300% modulus, elastic modulus, tear strength) after immersion. The ratio (%) is shown in Table 4.

(3) Solvent resistance test A test piece for measuring mechanical strength was immersed in (a) toluene, (b) ethyl acetate, and (c) isopropyl alcohol at 20 ° C for 1 week. Thereafter, the test piece was taken out, and the change in the weight of the test piece and the change in the test result by the mechanical strength test (1) were measured. The change in weight before and after immersion of the test piece (indication of swelling) and how much the original mechanical strength was lost was used as a solvent resistance test result. The evaluation results are based on the weight of the specimen before immersion and the mechanical strength test values (breaking strength, elongation at break, 100% modulus, 200% modulus, 300% modulus, elastic modulus, tear strength) after immersion. The ratios (%) are shown in Tables 5 to 7.

  In Tables 4 to 7, the tensile test results (breaking strength, breaking elongation, 100% modulus, 200% modulus, 300% modulus and elastic modulus) and tear test results (tear strength) values (with respect to the values of the test pieces before immersion) The arithmetic average of (ratio) was described as an average strength value, and was used as an index for a decrease in mechanical strength.

From Table 3, the following is clear. That is, in the mechanical strength evaluation (breaking strength, breaking elongation, 100% modulus, 200% modulus, 300% modulus, elastic modulus and tear strength) of the polyurethane elastomer, the polyester polyols of Examples 1 to 3 using the polyester polyol of the present invention were used. In this case, although slightly inferior to Comparative Example 1 using Polyol-4, which is a normal succinic polyester polyol, the physical properties thereof are not greatly impaired. However, the physical properties are clearly improved as compared with Comparative Example 2 using Polyol-5 with a large amount of castor oil and Comparative Example 3 using castor oil itself.

From Table 4, the following is clear. That is, in the water resistance evaluation of polyurethane elastomers, in Examples 1 to 3 using the polyester polyol of the present invention, the average strength value and weight change after immersion in water (60 ° C.) are normal succinic acid-based polyester polyols. Compared to Comparative Example 1 using

  Moreover, the following is clear from Tables 5-7. That is, in the solvent resistance evaluation of the polyurethane elastomer, in the case of Examples 1 to 3 using the polyester polyol of the present invention, it is slightly inferior to Comparative Example 1 using the normal succinic polyester polyol, Polyol-4. However, it does not greatly impair the physical properties. However, the physical properties are clearly improved as compared with Comparative Example 2 using Polyol-5 with a large amount of castor oil and Comparative Example 3 using castor oil itself.

  ADVANTAGE OF THE INVENTION According to this invention, the polyurethane elastomer excellent in solvent resistance and water resistance can be provided.

Claims (3)

Polyester polyol for polyurethane elastomer, which is obtained by dehydrating condensation with castor oil using succinic acid as a carboxylic acid component and mono or polyoxyalkylene glycol having a number average molecular weight of 400 or less as an alcohol component. Polyester polyol, wherein the polyester polyol has a hydroxyl value of 20 to 200 mg KOH / g, and the amount of castor oil used is 10 to 60% by weight with respect to the obtained polyester polyol.   The polyester polyol according to claim 1, wherein the mono- or polyoxyalkylene glycol having a number average molecular weight of 400 or less is diethylene glycol and / or triethylene glycol. A polyurethane elastomer obtained by reacting at least a polyisocyanate, a polyol and a crosslinking agent, wherein the polyester polyol according to claim 1 or 2 is used as at least a part of the polyol.