JPH0680105B2 - Method for producing polyurethane elastomer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a polyurethane elastomer, and more particularly to a method for producing a polyurethane elastomer using a specific high molecular weight diol.

[Prior Art] It is known to produce a thermoplastic polyurethane-based elastomer mainly using a high molecular weight diol, a chain extender, and a diisocyanate compound as essential raw materials. It is known to use polyoxyalkylene-based diols, especially polyoxypropylene diols and poly (oxypropylene-oxyethylene) diols as high molecular weight diols. These high molecular weight diols can be obtained at a lower production cost than polyoxytetramethylene diols and polyester diols, but the polyurethane elastomers obtained by using them have mechanical properties such as tensile strength and abrasion resistance. Will be insufficient. For example, JP-A-52-33
Japanese Patent No. 998 describes that a poly (oxypropylene-oxyethylene) diol having an oxyethylene group content of 15 to 50% by weight is reacted with diphenylmethane disocyanate and 1.4-butanediol to produce a polyurethane elastomer. ing. Is this poly (oxypropylene-oxyethylene) diol a block copolymer obtained by adding propylene oxide to a bifunctional initiator and then adding ethylene oxide?
Alternatively, it is a random copolymer obtained by reacting a mixture of propylene oxide and ethylene oxide with a bifunctional initiator.

[Problems to be Solved by the Invention] By using an inexpensive polyoxyalkylene diol, mechanical properties comparable to those of a polyurethane-based elastomer having high mechanical properties obtained by using polyoxytetramethylene diol or polyester diol can be obtained. It would be extremely useful if a polyurethane-based elastomer could be obtained.
As shown in the above-mentioned publicly known examples (see particularly Table 1 of Example 1), the higher the proportion of oxyethylene groups in the poly (oxypropylene-oxyethylene) diol, the higher the mechanical properties of the polyurethane elastomer. Tends to become. However, even the polyurethane-based elastomer obtained by using the poly (oxypropylene-oxyethylene) diol having an oxyethylene group of 30% by weight or 45% by weight shown in this Example is not completely satisfactory. It cannot be said that it has possible mechanical properties. It is generally known that the higher the oxyethylene group content of the polyoxyalkylene diol, the higher the hydrophilicity of the polyoxyalkylene diol. Therefore, it is considered that the polyurethane elastomer obtained by using the polyoxyalkylene diol having a high oxyethylene group content has extremely low water resistance.

[Means for Solving Problems] The present invention has been made to solve the above problems, uses inexpensive polyoxyalkylene diol, and has relatively high mechanical properties and excellent water resistance. The present invention provides a polyurethane-based elastomer, and has the following invention as its gist.

In a method for producing a polyurethane elastomer by using a high molecular weight diol, a chain extender and a diisocyanate compound as essential raw materials, ethylene oxide and propylene oxide and / or butylene oxide are used as the high molecular weight diol with a bifunctional initiator having a molecular weight of 250 or less. And a mixture of (ethylene oxide) / (propylene oxide and / or butylene oxide) in a mixing weight ratio of 60/40 to 90/10 is added to obtain a mixture of the ethylene oxide, propylene oxide and A method for producing a polyurethane-based elastomer, which comprises using a polyoxyalkylene-based diol having a total of at least 90% by weight of butylene oxide residues.

The feature of the present invention is to use a polyoxyalkylene diol having a random copolymer chain of ethylene oxide and propylene oxide and / or butylene oxide as a high molecular weight diol and having a high proportion of ethylene oxide residues (ie, oxyethylene groups). There is a point to do. For example, poly (oxyethylene-oxypropylene) obtained by using ethylene oxide and propylene oxide.
The present invention will be described below by taking a diol as an example.

Obtained by first adding propylene oxide and then ethylene oxide to the bifunctional initiator, or conversely first adding ethylene oxide and then propylene oxide, and the addition weight ratio of ethylene oxide / propylene oxide is 60/40 to The polyurethane elastomer obtained by using a block copolymer poly (oxyethylene-oxypropylene) diol having a ratio of 90/10 has extremely low water resistance. Moreover, the random copolymer poly (oxyethylene-oxypropylene) in the present invention is used.
The mechanical properties are obviously lower than those of the polyurethane elastomer obtained by using the diol. The reason for this is that the presence of a long chain of oxyethylene groups makes the poly (oxyethylene-oxypropylene) diol extremely hydrophilic, whereas even if the content of oxyethylene groups in the whole is the same, It is considered that the hydrophilicity does not become so high when the group chain is separated by the oxypropylene group, and the mechanical properties of the elastomer are also expected to be related to the chain length of the oxyethylene group. Similarly, even if a poly (oxyethylene-oxypropylene) diol obtained by adding a mixed alkylene oxide of ethylene oxide and propylene oxide and then adding ethylene oxide to a bifunctional initiator is used, its terminal oxyethylene group Due to the existence of the chain, a polyurethane elastomer having sufficient physical properties such as water resistance cannot be obtained. In the poly (oxyethylene-oxypropylene) diol of the present invention, the higher the oxyethylene group content, the lower the water resistance tends to be, but conversely the mechanical properties tend to be improved. On the other hand, the higher the oxyethylene group content is, the higher the melting point of poly (oxyethylene-oxypropylene) diol is.
Inconvenient to handle.

Further, the polyurethane-based elastomer obtained by using the polyoxyalkylene-based diol having a high proportion of oxypropylene groups has a small difference between the melting point and the decomposition initiation temperature, and therefore, there are many restrictions in melt-processing it. For example, the range of molding temperatures that can be used in injection molding and extrusion molding is narrow, and in fact injection molding and extrusion molding of polyurethane elastomers obtained by using polyoxypropylene diol were almost impossible. On the other hand, the polyurethane elastomer obtained by using the poly (oxyethylene-oxypropylene) diol having a high oxyethylene group content in the present invention has a large difference between the melting point and the decomposition initiation temperature, and therefore is easily melt-processed and injected. It enables molding and extrusion molding. In the present invention, butylene oxide (that is, 1.2-butylene oxide and / or 2.3-butylene oxide) may be used instead of or as a part of the propylene oxide. A polyoxyalkylene-based diol using butylene oxide instead of propylene oxide remarkably improves the water resistance but tends to lower the mechanical properties.

Hereinafter, the polyoxyalkylene-based diol in the present invention will be described in more detail. In the following, EO refers to both ethylene oxide and oxyethylene groups, and PO refers to propylene oxide and oxypropylene groups (that is, 1.2-
Both oxypropylene groups) and BO refer to butylene oxide and oxybutylene groups (ie 1.2-oxybutylene groups and / or 2.3-oxybutylene groups). PO-BO means (PO and / or BO). The polyoxyalkylene-based diol in the present invention contains EO as a bifunctional initiator.
It is obtained by adding a mixture of PO-BO. The mixing weight ratio in this mixture is 60/40 to 90 expressed as EO / PO-BO.
It is necessary to be / 10, especially 60 / for the above reasons.
It is preferably 40 to 80/20. Addition of this mixed alkylene oxide followed by EO to form a long EO end chain is not preferred as described above. Even if the EO addition is carried out at the end, the amount should not be more than about 3% by weight of the total polyoxyalkylene-based diol, and even if it is done, it is substantially 0 (that is, less than about 1% by weight).
Is preferred. On the contrary, it is possible to add a small amount of PO or BO after the addition of the mixed alkylene oxide.
However, it is suitable that the amount thereof is 10% by weight or less, and even if it is performed, it is preferably about 5% by weight or less. Of course, addition of EO, PO or BO after addition of mixed alkylene oxides does not bring about a very advantageous effect, and therefore it is most preferable not to perform addition of these alkylene oxides after addition of mixed alkylene oxides. The mixed alkylene oxide can be added in two or more stages.
The mixed alkylene oxide in each stage may be one in which the type and mixing ratio of each alkylene oxide is changed.

The proportion of the mixed alkylene oxide residues in the polyoxyalkylene-based diol of the present invention is at least 90.
% By weight. The remaining 10% by weight or less is the residue of the bifunctional initiator or the sum of it and the residue of the alkylene oxide added after the above mixed alkylene oxide addition. As the bifunctional initiator, a dihydroxy compound (divalent alcohol or phenol) or a divalent amine is suitable, and a dihydroxy compound is particularly preferable. The dihydric alcohol includes aliphatic dihydric alcohols, alicyclic dihydric alcohols, dihydric alcohols having an aromatic nucleus, and the dihydric phenols include mononuclear diphenols and polynuclear diphenols. Preferred are aliphatic dihydric alcohols such as alkylene diols having 2 to 6 carbon atoms and mono- or polyoxyalkylene diols. Specifically, ethylene glycol, diethylene glycol and other polyethylene glycols, propylene glycol, dipropylene glycol and other polypropylene glycols, aliphatic compounds such as 1.4-butanediol, 1.2-butylene glycol, neopentyl glycol, and 1.6-hexanediol. Two
Examples thereof include dihydric alcohols, alicyclic dihydric alcohols such as cyclohexylenediol and cyclohexanedimethanol, and dihydric phenols such as bisphenol A and bisphenol S. The polyoxyalkylene glycol as a bifunctional initiator has EO and PO, and particularly those having a large amount of EO bring about an increase in the EO chain as a whole polyoxyalkylene diol. Therefore, when polyethylene glycol or an EO-containing compound is used as the bifunctional initiator, the ratio of the EO residue to the total polyoxyalkylene diol is preferably less than about 5% by weight,
Particularly, it is preferably less than about 3% by weight. The proportion of residues of other bifunctional initiators is less than 10% by weight, as described above. The bifunctional initiator in the present invention has a molecular weight of 250 or less. Especially ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol,
Tripropylene glycol, 1.4-butanediol and
It is 1.6-hexanediol. The bifunctional initiator can be used in combination of two or more kinds.

A polyoxyalkylene-based diol is obtained by adding the alkylene oxide to the above-mentioned bifunctional initiator in the presence of a catalyst. Examples of the catalyst include alkali metal hydroxides, oxides, carbonates and the like, basic catalysts such as tertiary amines, and acidic catalysts such as boron trifluoride and heteropolyacids. The hydroxyl value of the obtained polyoxyalkylene-based diol is suitably 25 to 120 (molecular weight of about 4500 to 900), and particularly preferably about 40 to 80 (molecular weight of about 2800 to 1400).
Further, the polyoxyalkylene-based diols in the present invention can be used in combination of two or more kinds. Further, two or more kinds of polyoxyalkylene-based diols in the present invention can be used in combination. Furthermore, the polyoxyalkylene-based diol in the present invention can be used in combination with a small amount of other high-molecular-weight diol as long as the mechanical properties of the polyurethane-based elastomer obtained by using the same are not significantly reduced.

The chain extender is a divalent low molecular weight compound and is composed of a low molecular weight diol or diamine. Its molecular weight is about 300
The following is suitable, and about 200 or less is particularly preferable. The diol is preferably an aliphatic dihydric alcohol or an alicyclic dihydric alcohol having a primary hydroxyl group, and the diamine is an aliphatic, alicyclic or aromatic diamine. Specifically, for example, the diols, alkylenediamines, isophoronediamines, and MOCAs listed above as the bifunctional initiators.
and so on. Particularly, an aliphatic dihydric alcohol having 2 to 6 carbon atoms is preferable, and ethylene glycol, 1.4-butanediol, neopentyl glycol, and dipropylene glycol are most preferable.

The amount of the chain extender used is appropriately 1 to 15 times mol, and preferably about 2 to 10 times mol, based on 1 mol of the high molecular weight diol. Most preferably, about 3 to 8 times the molar amount is most preferable.

As the diisocyanate compound, various aromatic, aliphatic, or alicyclic diisocyanate compounds can be used. For example, diphenylmethane diisocyanate,
Examples include tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and methylene bis (cyclohexyl isocyanate). Further, the isocyanate compound may be a substantially divalent isocyanate-containing compound modified by various compounds or treatments. Further, two or more kinds of these diisocyanate compounds may be used in combination. The amount of the diisocyanate compound used is appropriately 0.8 to 1.2 mol, and particularly preferably about 0.9 to 1.1 mol, based on the total number of moles of the high molecular weight diol and the chain extender.

The polyurethane-based elastomer is obtained from the above-mentioned three essential raw materials, but other auxiliary raw materials may be used in combination. Examples of the auxiliary material include a catalyst, a filler, a reinforcing material, a stabilizer, a coloring agent, a cross-linking agent, and a foaming agent. Organometallic compounds (particularly organotin compounds) and tertiary amines are suitable as the catalyst. An inorganic or organic powder is suitable as the filler, and a fibrous or flat filler is suitable as the reinforcing material. As the stabilizer, one kind or two or more kinds of an ultraviolet absorber, a light stabilizer and an antioxidant is used. The cross-linking agent has a reactive functional group (that is, hydroxyl group, amino group, isocyanate group, etc.) 3
There are compounds having the above, and it is preferable that they are substantially not used as described below. A polyurethane-based elastomer foamed by using a foaming agent such as water or a halogenated hydrocarbon-based foaming agent can be produced, but the amount thereof is about 10% by weight or less, particularly about 5% by weight or less based on all essential raw materials. preferable.

Using the above raw materials, one-shot method, prepolymer method,
The polyurethane elastomer is manufactured by a method such as a quasi-prepolymer method. A usual one-shot method or a one-shot method called a reaction injection molding method can be adopted, but in the present invention, it is particularly preferable to adopt a prepolymer method or a quasi-prepolymer method. In the case of the prepolymer method or the quasi-prepolymer method, a solvent can be used to form the elastomer. The polyurethane elastomer obtained by the present invention is usually a thermoplastic elastomer. By using the above-mentioned cross-linking agent together, a polyurethane-based elastomer having a cross-linked polymer structure (what is commonly called a thermosetting polyurethane-based elastomer) can be obtained. However, in the present invention, a thermoplastic polyurethane-based elastomer is particularly preferable in terms of mechanical properties. Although a thermoplastic polyurethane elastomer can be produced by using a small amount of a crosslinking agent, a crosslinking agent is not usually used. During the production of polyurethane elastomers, it is possible to directly obtain sheets, films, and other molded articles by casting, etc. Also, once manufacture a molding material consisting of polyurethane elastomer powders and particles, and extrude this. It is also possible to manufacture a molded product by injection molding or injection molding.

The present invention will be specifically described below with reference to examples and the like, but the present invention is not limited to these examples.

[Synthesis example] I In a pressure-resistant autoclave made of stainless steel with 5 volumes, 268 g of dipropylene glycol and 25 g of 48% caustic solution in water.
Was charged under a nitrogen atmosphere, the temperature was raised to 120 ° C., and water was distilled off under reduced pressure. Then a mixture of EO and PO in a weight ratio of 60/40
3,850 g was introduced over 4 hours while maintaining the temperature at 120 ° C. Further, the mixture was kept at 120 ° C. for 1 hour, and the unreacted alkylene oxide mixture was distilled off under reduced pressure. Magnesium silicate was added to adsorb the catalyst, filtered and dried to obtain a product. The hydroxyl value of the obtained diol was 56.3 mg KOH / g, which was a colorless transparent liquid. Hereinafter, the obtained diol is referred to as diol E.

Diols C, D, F, I and J were prepared by the same method as above but with different EO / PO weight ratios. Similarly for PO instead of BO
Diol L was prepared using (1.2-butylene oxide).

The physical properties of these diols are shown in Table 1 below.

II In the same manner as in Synthesis Example I, except that the alkylene oxide was not a mixture, 2,118 g of PO was introduced and reacted first, and then 1,732 g of EO was introduced and reacted in the apparatus, raw materials and procedure of Synthesis Example I. Was synthesized. The resulting diol is called diol B.

Diol G was prepared by the same method except that the weight ratio of PO and EO was changed. Also, diol H was produced in the same manner by changing the reaction order of PO and EO.

The physical properties of these diols are shown in Table 1 below.

III Diol A and diol K were produced in the same manner as in Synthesis Example I using only PO or EO as the alkylene oxide. The physical properties of these diols are shown in Table 1 below.

In Table 1, "EO / PO" or "EO / BO" in the "Type of alkylene oxide" column indicates that EO and PO (or BO) are mixed and reacted. PO → EO "
Indicates that EO was reacted after the PO reaction, and "EO → PO" is
Indicates that PO was reacted after the EO reaction.

For comparison, the following commercially available diols M and N were used.

Diol M: polyoxytetramethylene glycol with a hydroxyl value of about 56 mg KOH / g (Mitsubishi Chemical Co., Ltd .: “PTMG-200
0 ") Diol N: poly (1.4-butylene adipate) diol with a hydroxyl value of about 56 mg KOH / g (manufactured by Nippon Polyurethane Co., Ltd .:
"N-4010") Examples and Comparative Examples To 100 parts of the above-mentioned diols A to N, 77,8 parts of 4,4'-diphenylmetallisisocyanate (MDI) was added, and the mixture was maintained at 80 ° C for 3 hours while stirring in a nitrogen atmosphere. A polymer was obtained. Then, the prepolymer adjusted to 70 ° C. was added with 1.4.
Butanediol (22,2 parts) was added, and the mixture was defoamed under reduced pressure with stirring, poured into a mold at 80 ° C, and cured at 130 ° C for 5 hours. The obtained polyurethane elastomer sheet is at 25 ° C,
After standing still for 7 days in an atmosphere of humidity 50, various physical properties were measured. The results obtained are shown in Table 2 below.

Examples 1 to 4 have a larger tensile strength than Comparative Examples 1 to 6,
Further, it has excellent water resistance as compared with Comparative Example 7. Example 5
Has particularly excellent water resistance.

Compared to the polyester diol of Comparative Example 9, the mechanical characteristics were slightly inferior, but it was found that it has excellent water resistance and has the same balanced physical properties as the polyoxytetramethylene diol of Comparative Example 8. .

EFFECTS OF THE INVENTION The present invention makes it possible to obtain a polyurethane-based elastomer having excellent balanced mechanical properties such as polytetramethylene glycol and excellent mechanical properties and water resistance from an inexpensive polyether-based diol. In the past, it has become possible to apply to fields where polyether polyurethane elastomers are conventionally unsuitable. For example, application to cast products such as conveyor sheets and rolls and films becomes easy.

In addition, application to adhesives and coating materials is also conceivable.

 ─────────────────────────────────────────────────── --Continued from the front page (56) References JP 59-1523 (JP, A) JP 59-145129 (JP, A) JP 56-133143 (JP, A) JP 52- 33998 (JP, A) JP-A-57-42715 (JP, A) JP-B-63-52045 (JP, B2)

Claims (2)

[Claims] 1. A method for producing a polyurethane elastomer using a high molecular weight diol, a chain extender, and a diisocyanate compound as essential raw materials, wherein as the high molecular weight diol, ethylene oxide and propylene oxide are used as a bifunctional initiator having a molecular weight of 250 or less. And / or a mixture with butylene oxide and obtained by adding a mixed alkylene oxide having a mixing weight ratio of (ethylene oxide) / (propylene oxide and / or butylene oxide) of 60/40 to 90/10, A method for producing a polyurethane-based elastomer, which comprises using a polyoxyalkylene-based diol in which the total of the residues of ethylene oxide and propylene oxide and / or butylene oxide is at least 90% by weight. 2. The mixing weight ratio of (ethylene oxide) / (propylene oxide and / or butylene oxide)
The method of claim 1 wherein the method is 60 / 40-80 / 20.