JP2000128948A - Production of thermosetting polyurethane resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce the subject polyurethane resin without eluting a metal catalyst to the outside of the system by using an isocyanate group-terminated prepolymer or a polyol having an alkoxytitanate structure in the molecule. SOLUTION: (A) A polyol having an alkoxytitanate structure in the molecule is reacted with a polyisocyanate in excess of isocyanate groups to thereby provide an isocyanate group-terminated prepolymer having the alkoxytitanate structure in the molecule. For example, (B) a tetraalkyl titanate (e.g. tetrapropyl titanate) is reacted with a polyol without containing a titanate (e.g. polyethylene glycol) to afford a polyol having the alkoxytitanate structure in the molecule. The objective resin is produced by, e.g. a method for using both the components A and B and reacting the component A with a short-chain polyol. Since the resultant resin has the titanate group having catalyst effects in the polymer, elution preventing effects on the catalyst are achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a thermosetting polyurethane resin. Further, the present invention relates to a thermosetting polyurethane resin from which a metal catalyst does not elute.

[0002]

2. Description of the Related Art The composition and production method of a thermosetting polyurethane resin are outlined in "Polyurethane resin" published by Nikkan Kogyo Shimbun (Keiji Iwata, 1969). The thermosetting polyurethane resin may not use a metal catalyst at all in consideration of heat resistance, hydrolysis resistance, and safety of the obtained resin. In the method without such a catalyst, the progress of the urethanization reaction is slow, and the productivity is poor such as a long curing time.
There have been problems such as insufficient urethane formation reaction resulting in insufficient resin strength. Therefore, a method using a catalyst has been conventionally used, and as the catalyst, a tertiary amine, a tin-based catalyst, and other organic metals have been used alone or in combination. These are generally low molecular weight compounds and have the risk of eluting into water or alcohol. In particular, it is an extremely important condition for thermosetting polyurethane resins used for artificial organs and the like that the amount of eluted substances is small. As a tertiary amine catalyst, an amine catalyst having a hydroxyl group has been studied as a method for solving residual odor and fogging on a glass surface caused by liberation of the catalyst.

[0003] Metal catalysts that promote urethane formation include:
Various metal compounds are known. The most common are divalent or tetravalent organotin compounds. Other than the tin compound, there are various metal compounds such as an alkali metal compound, an alkaline earth metal compound, and a transition metal compound, and a titanium compound is also included. Particularly, tetraalkyl titanates such as tetrapropyl titanate and tetrabutyl titanate as organic titanium compounds have been found to have a very effective catalytic effect on the urethanization reaction. However, these compounds easily react with water in the air to form insoluble titanium oxide or a titanium oxide polymer and have poor stability. Therefore, these compounds are rarely used for the purpose of a urethanization reaction catalyst. There are no applications in which titanium is incorporated into the molecule for the purpose of accelerating the reaction.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to produce a thermosetting polyurethane resin having excellent physical properties without the catalyst used in the reaction being eluted and withstanding long-term use.

[0005]

Means for Solving the Problems In order to solve the above-mentioned problems, as a result of intensive studies, these tetraalkyl titanates were incorporated into the molecule of the isocyanate prepolymer or
Incorporated in the molecule of the polyol used as a curing agent,
The present inventors have found a method for producing a thermosetting polyurethane which has stable reactivity and long-term storage, and further minimizes elution by a solvent after polyurethane molding, and has completed the present invention. That is, the present invention has an alkoxy titanate structure in the molecule,
This is a method for producing a thermosetting polyurethane resin, characterized by using an isocyanate group-terminated prepolymer or a polyol.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in more detail.
An isocyanate group-terminated prepolymer having an alkoxy titanate structure in the molecule is obtained by reacting a polyol having an alkoxy titanate structure in the molecule with a polyisocyanate in an isocyanate group excess of at least a molar ratio of isocyanate group / hydroxyl group of 1 or more.

There are various methods for obtaining a polyol having an alkoxy titanate structure in the molecule, and a preferred method is a reaction between a tetraalkyl titanate and a polyol containing no titanate.
As the tetraalkyl titanate, one having an alkyl group having 1 to 5 carbon atoms is preferable, and tetrapropyl titanate, tetrabutyl titanate, and the like are particularly preferable because those having a high purity can be easily obtained by distillation. This reaction is carried out after mixing the titanium compound and a polyol not containing the titanium compound, at 100 ° C. or higher, preferably 1 ° C.
It is carried out by distilling propyl alcohol, butyl alcohol, and the like released by the exchange reaction out of the system at normal pressure or under vacuum while heating to 30 ° C. or more. It is considered that these alkoxy titanates form a polyol represented by the following general formula (1) by removing monoalcohol by exchange reaction with a large excess of the polyol and reacting with the polyol.

(HO-RO-) ₄ Ti (1) wherein R is a polyol residue

There is no limitation on the content of titanium,
Preferably 0.1 pp on a weight basis relative to the polyol
m, preferably 1 ppm.

[0010] The polyol containing no titanium compound used in the present invention is not particularly limited as long as it is a polyol used in polyurethane chemistry. Examples of the polyol include polyester polyol, polycaprolactone polyol, polycarbonate polyol, polyether polyol, polybutadiene polyol, castor oil and its derivative polyols, and other glycols, for example, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, pentanediol, Heptanediol, hexanediol,
Glycerin, neopentyl glycol, di- or polypropylene glycol, trimethylolethane, trimethylolpropane, monoethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N, N, N ', N'-tetraethylene glycol diamine, etc. Can be mentioned. These polyols have a molecular weight of 62 or more and a number average molecular weight of 5000 or less. The polyol for the isocyanate group-terminated prepolymer preferably has a number average molecular weight of 500 to 5,000, and the polyol for the curing agent has a number average molecular weight of 62 to 5,000.
2000 is preferred.

The polyester polyol is obtained by a polycondensation reaction between a dicarboxylic acid and an acid anhydride thereof and a diol. The polyol used for producing the polyester polyol is, specifically, ethylene glycol, diethylene glycol, 1,2-propylene glycol,
3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol (hereinafter abbreviated as 1,4-BG), 1,5-pentane glycol, 2-methyl-1, 3-propylene glycol, 2-methyl-1,4-butylene glycol,
1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, neopentyl glycol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2- Hexyl-1,3-propanediol and the like, which may be used alone or in combination.

Examples of the dicarboxylic acids include carboxylic acids such as succinic acid, adipic acid, sebacic acid, azelaic acid, dimer acid, orthophthalic acid, isophthalic acid, and terephthalic acid, acid esters thereof, and acid anhydrides thereof. These may be used alone or in combination. Also,
Polycaprolactone diol, castor oil and its derivatives are also included as oxycarboxylic acid polymers.

The polycarbonate polyol is 1,4-B
G, 1,5-pentane glycol, 2-methyl-1,3
Obtained by the reaction of propylene glycol, 2-methyl-1,4-butylene glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,9-nonanediol with a diaryl carbonate or dialkyl carbonate. It is a bifunctional hydroxyl-terminated polycarbonate having a molecular weight of 500 to 5,000.

The polyether polyol is a polyol represented by polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like.

Castor oil and its derivatives may be dehydrated castor oil, or a product obtained by replacing glycerin with another polyol in a transesterification reaction.

The polyisocyanate used in the present invention is hexamethylene diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, paraxylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate (hereinafter referred to as MDI).
), Isocyanates such as polyphenylmethane polyisocyanate and naphthylene diisocyanate, and prepolymers and derivatives thereof.

The polyol having an alkoxy titanate structure in the molecule may be used as an isocyanate group-terminated prepolymer by reacting with a polyisocyanate.
You may use as it is for manufacture of a thermosetting polyurethane resin.

On the other hand, even if tetrapropyl titanate or tetrabutyl titanate is directly added to the isocyanate, it is difficult to mix uniformly, and there is a method of diluting and mixing with an additive such as a solvent or a plasticizer. It is also conceivable that as it is, it elutes from the molded product to the surface. For example, the presence of a mixture in a polyol is easily confirmed by gas chromatography, but the presence of titanium in the molecule is incorporated in the polyol molecule, although the presence of titanium is confirmed by emission spectroscopy. The titanate compound is difficult to elute and evaporate and is hardly detected as a single component.

There are three methods for producing a thermosetting polyurethane resin using an isocyanate group-terminated prepolymer or polyol having an alkoxy titanate structure in the molecule. One is a so-called prepolymer method in which a long-chain polyol and a polyisocyanate are reacted by the most general method to form an isocyanate group-terminated prepolymer, and the prepolymer and the short-chain polyol are reacted to obtain a resin. Another method is a so-called one-shot method in which a long-chain polyol, a short-chain polyol, and a polyisocyanate are reacted at one time. Further, as an intermediate method between them, there is a so-called semi-one-shot method in which a curing agent comprising a mixture of an isocyanate group-terminated prepolymer, a long-chain polyol and a short-chain polyol, in which a long-chain polyol is also added to the curing agent, is reacted. The present invention is effective in any of the above methods.

[0020]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention should not be construed as being limited to Examples. "Parts" and "%" shown below are parts by weight and% by weight, unless otherwise specified. Example 1 Polyethylene adipate diol (number average molecular weight = 10
After 100 ppm of tetrapropyl titanate was added to 00), the mixture was reacted at 160 ° C. The obtained polyester polyol is a colorless room temperature solid and has a hydroxyl value of 75.1 KOHmg / g,
At an acid value of 0.3 KOH mg / g and a viscosity of 350 mPa · s / 75 ° C., it was no different from ordinary polyester. Gas chromatographic analysis showed no tetrabutyl titanate. Before the reaction in which polyethylene adipate was mixed with tetrapropyl titanate, a peak of tetrapropyl titanate corresponding to the added amount was observed by gas chromatography. By reacting 746 parts of this polyethylene adipate diol with 254 parts of MDI, an isocyanate group-terminated prepolymer was obtained. The isocyanate content of this prepolymer was 4.30%. 100 parts of the thus-obtained isocyanate-terminated prepolymer having an alkoxy titanate structure in the molecule is reacted with 4.0 parts of dehydrated 1,4-BG. The mixture was heated and melted, degassed under a vacuum of 5 to 10 mmHg for 30 minutes, and mixed with 1,4BG heated to 60 ° C while rapidly stirring. The sheet was previously placed in a sheet forming mold having a thickness of 3 mm at 140 ° C. The reaction progressed rapidly by mixing the isocyanate and the polyol, but the pot life was about 4 minutes, so the injection was completed within that time. After about 15 minutes, the sheet was removed from the sheet mold and further after-cured at 140 ° C. for 3 hours to obtain a thermosetting polyurethane resin. The hardness and mechanical properties of this resin were as follows. JIS A = 72, tensile strength (hereinafter abbreviated as TB) 58.5 MPa, elongation at break (hereinafter E
B) 600%, tear strength (hereinafter abbreviated as TR) 70
N / mm

Example 2 0.1 part of tetrabutyl titanate was added to 100 parts of 1,4-BG, and the mixture was stirred at 150 ° C. and a vacuum of 20 mmHg to react for 60 minutes. The reaction product was analyzed by gas chromatography, and no peak of tetrabutyl titanate was observed. 1,4 obtained in this way
-BG was reacted with the isocyanate group-terminated prepolymer of Example 1 in the same manner as a curing agent. Although the reaction proceeds more rapidly than in Example 1 by mixing the isocyanate and the polyol, the pot life was about 3 minutes and the injection into the mold had to be performed promptly. After about 15 minutes, the resin was taken out of the mold, and after-cured at 140 ° C. for 3 hours to obtain a thermosetting polyurethane resin. The hardness and mechanical properties of this resin were as follows. JIS A = 73, TB = 59.0
MPa, EB = 610%, TR = 70N / mm

Example 3 Refined castor oil (viscosity 1000 mPa · s / 25 ° C., hydroxyl value 168 KOHmg / g, acid value 2.0 KOHmg / g) 100
0 g and polytetramethylene glycol (number average molecular weight 6
Then, 0.30 g of tetrabutyl titanate is further added, and a transesterification reaction is performed at a temperature of 180 ° C. The generated glycol is 10mm
The mixture was reacted for about 6 hours while discharging the system under a vacuum of Hg to synthesize a modified castor oil. This modified castor oil has a hydroxyl value of 1
12 KOHmg / g, acid value 0.5 KOHmg / g or less, viscosity 24
00 mPa · s / 40 ° C. Gas chromatographic analysis did not show any peak for tetrabutyl titanate. 308 g of this modified castor oil and liquid MDI (Coronate 4400, manufactured by Nippon Polyurethane Industry; NCO content =
479 g of MDI and 213 g of MDI were reacted at 80 ° C. for 3 hours to synthesize an isocyanate group-terminated prepolymer. The isocyanate group-terminated prepolymer obtained had an isocyanate content of 18.1% and a viscosity of 2000 mPa · s /
25 ° C. Separately, 800 g of refined castor oil and 200 g of quadrol (polyol obtained by adding four propylene oxides to ethylenediamine) were mixed to prepare a curing agent A. 55 parts of the isocyanate group-terminated prepolymer at a liquid temperature of 25 ° C. and 45 parts of a curing agent were mixed, poured into a cylindrical cup, and the gelation time was observed. Gelation was observed 6 minutes and 30 seconds after the start of the stirring and mixing was started.
Further, a change in hardness was followed by curing in a heat-insulating container at 40 ° C., but the hardness was stabilized after about 16 hours. After left for one week at room temperature, the hardness of the molded product was measured. The hardness of the molded product was 84 according to JIS A.

Example 4 To 200 g of quadrol was added 0.1 g of tetrabutylentinitanate, and the mixture was added at 140 ° C. under a vacuum of 20 mmHg for about 3 hours.
The reaction was performed for 0 minutes. Hardening agent B was prepared by mixing 800 g of refined castor oil with a water content of 0.01% or less.
Isocyanate-terminated prepolymer of Example 3 and curing agent B
Was reacted under the same conditions as in Example 3 to compare gelation and curing. Gelation was about 4 minutes and 30 seconds. Further, the change in hardness was traced by curing in a 40 ° C. heat storage, but the hardness of the molded product was stabilized after about 12 hours. Furthermore, after leaving at room temperature for one week, the hardness of the molded article was measured. The hardness of the molded product is JIS
A was 85. 100 g of the cured product was pulverized into small pieces of 3 mm or less, immersed in 100 ml of warm water (40 ° C.) for 30 hours, separated by filtration, and a catalyst eluted into the warm water was measured by an ICP emission spectrometer. It was 1 ppm or less.

Comparative Example 1 Polyethylene adipate diol (number average molecular weight 150
0) 746 parts of MDI and 254 parts of MDI were reacted to obtain an isocyanate group-terminated prepolymer. The isocyanate content of this prepolymer was 4.32%. 100 parts of this isocyanate-terminated prepolymer and 1,1 dehydrated
4.0 parts of 4-BG was reacted under the same conditions as in Example 1. The isocyanate group-terminated prepolymer is heated and melted at 110 ° C., degassed under a vacuum of 5 to 10 mmHg for 30 minutes,
To this, 1,4-BG heated to 60 ° C. is mixed with rapid stirring. The mixture was poured into a mold heated to 140 ° C. in advance and subjected to reaction molding. The reaction progressed rapidly by mixing the isocyanate and the polyol, but the pot life was about 9 minutes or more. After about 30 minutes, it was impossible to remove the resin from the mold. However, after curing was further performed at 140 ° C. for 3 hours, the resin was removed from the mold to obtain a thermosetting polyurethane resin. The hardness and mechanical properties of this resin were as follows. JIS A = 70, TB = 57.0MPa, EB = 540%, T
R = 68N / mm

Comparative Example 2 Refined castor oil (viscosity 1000 mPa · s / 25 ° C.), hydroxyl value 168 KOHmg / g, acid value 2.0 KOHmg / g) 100
0 g and tetramethylene glycol (hydroxyl value 180 KOH
mg / g) 2000 g of paratoluenesulfonic acid 0.10
g as a transesterification catalyst at 180 ° C to 200 ° C, 10
The reaction was carried out until the hydroxyl value became 120 or less while discharging glycerin generated under vacuum conditions of mmHg to the outside of the system. About 1
After 6 hours, the hydroxyl value is 118 KOHmg / g, the acid value is 0.5 K
A modified castor oil having an OH mg / g and a viscosity of 2450 mPa · s / 40 ° C. was obtained. 405 g of this modified castor oil and Example 3
479 g of liquid MDI and 213 g of MDI were reacted at 80 ° C. for 3 hours to synthesize an isocyanate group-terminated prepolymer. The isocyanate group-terminated prepolymer has an isocyanate content of 18.0% and a viscosity of 2200 mPa · s / 25.
It was a pale yellow transparent liquid at ℃. Separately refined castor oil 800
g and Quadrol 200 g were uniformly mixed to prepare a curing agent C. 55 parts of the isocyanate-terminated prepolymer at a liquid temperature of 25 ° C. and 45 parts of the curing agent C were mixed, poured into a cylindrical cup, and the increase in viscosity was observed. Gelation was observed 25 minutes after the start of the stirring and mixing with the start of the reaction. 4 more
The change in hardness was followed by curing in a heat storage at 0 ° C., but the hardness was stabilized after about 40 hours. Further, after being left at room temperature for one week, the hardness was measured. The hardness of the molded product was 82 according to JIS A.

[0026]

The moldability of polyurethane is important in industry. In particular, shortening the curing time improves productivity and leads to cost reduction. Further, by using a specific catalyst in the reaction between the isocyanate and the polyol, a side reaction is suppressed, and the mechanical properties of the molded product are improved. Further, since the urethanization reaction is promoted more than the ureaization reaction and the reaction with moisture is suppressed, there is an effect of reducing molding defects caused by bubbles due to carbon dioxide gas. This is a method for producing an environment-friendly thermosetting polyurethane resin, in which a titanate group having a catalytic effect is retained in the molecule of a polymer so that the catalyst does not elute out of the system and is environmentally friendly.

Claims (1)

[Claims] 1. A method for producing a thermosetting polyurethane resin, comprising using an isocyanate group-terminated prepolymer or polyol having an alkoxy titanate structure in a molecule.