JPH1135652A - Polyurethane-based elastomer composition for casting and its molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a transparent polyurethane-based elastomer and its moled products excellent in wear resistance and water resistance at comparatively high hardness, though rapidly curing at the temperature of metallic molds, during casting, of 50-100 deg.C. SOLUTION: This polyurethane-based elastomer composition for casting composes (the A solution) an urethane prepolymer having isocyanate groups at its terminals, obtained by reacting carbodiimide-modified diphenylmethanediisocynate with polytetramethylene ether glycol, (the B solution) glycol including 1,4-butanediol and neopentylglycol, a catalyst and, as necessary, a curing agent containing polytetramethylene ether glycol, wherein, neopentylglycol contained in the B solution is 1-70 mol.% with respect to 1,4- butanediol. Molded products can be obtained by casting and curing this composition and has a light transmittance of >=60% at a thickness of 2 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyurethane elastomer composition for casting and a molded article thereof. More specifically, the present invention relates to a polyurethane elastomer composition for casting comprising a specific urethane prepolymer and a curing agent containing a specific glycol component, and a molded article thereof. The composition of the present invention can be molded at a mold temperature of 100 ° C. or less,
The obtained molded article is transparent and fast-curing, but has relatively high hardness, and is excellent in wear resistance and water resistance.

[0002]

2. Description of the Related Art Polyurethane elastomer cast products using polytetramethylene ether glycol are excellent in abrasion resistance, mechanical properties, dynamic physical properties, solvent resistance, oil resistance, ozone resistance, etc. In addition to industrial parts such as paper, rolls and casters, OA equipment parts such as paper feed rolls and rolls for copiers, they are widely used in sports and leisure goods. In recent years, demands for transparent elastomers have been increasing in terms of aesthetics and decoration.

[0003] As a casting method of a polyurethane elastomer, a mixture of a urethane prepolymer having an NCO group (isocyanate group) at a terminal and a chain extender is injected into a mold, cured for a predetermined time, and then demolded. There are known ways to do this. As a polyurethane elastomer composition which gives such a cast product, a prepolymer of tolylene diisocyanate (hereinafter abbreviated as TDI) and polytetramethylene ether glycol can be added to MOCA (3,3'-dichloro-4,4'-diaminodiphenylmethane). ) Is most typical. However, TDI in raw materials is said to cause bronchial asthma and eczema, and aromatic diamines such as MOCA are said to have a risk of carcinogenesis. It is a serious problem.

On the other hand, an elastomer composition in which polytetramethylene ether glycol and 1,4-butanediol are used as a curing agent for a prepolymer of diphenylmethane diisocyanate and polytetramethylene ether glycol is also known (JP-A-55-9822). And widely used, but it is difficult to obtain a transparent polyurethane elastomer having high crystallinity in the resulting molded article. Japanese Unexamined Patent Publication No. 8-283368 discloses an elastomer of this type having improved transparency, in which a prepolymer of diphenylmethane diisocyanate and polytetramethylene ether glycol has a carbon number of 1,4-butanediol and an alkyl side chain. Transparent cast polyurethane-based elastomers using a curing agent containing 3 to 8 glycols and molded articles thereof have been proposed.

[0005]

However, in the case of the elastomer disclosed in the above publication, the mold temperature must be set to 120 ° C. or higher. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to mold at a mold temperature of 100 ° C. or lower, a fast-curing polyurethane elastomer composition for casting and a relatively high hardness. An object of the present invention is to provide a transparent molded article having excellent wear resistance and water resistance.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, 1,4-butanediol and neopentyl glycol were added to a prepolymer made from modified diphenylmethane diisocyanate as a raw material. It has been found that a transparent elastomer can be obtained even when the mold temperature is 100 ° C. or lower by using a curing agent containing the same, and the present invention has been completed.

That is, the gist of the present invention is as follows. (Solution A) isocyanate group-terminated urethane prepolymer obtained by reacting carbodiimide-modified diphenylmethane diisocyanate with polytetramethylene ether glycol, (Solution B) glycol containing 1,4-butanediol and neopentyl glycol and a catalyst. And a curing agent contained therein, wherein the ratio of neopentyl glycol to 1,4-butanediol in the solution B is 1 to 70 mol%. . The composition described in section 2.1 is cast, and then cured to have a hardness of 70 or more according to JIS K6301 (A standard), a rebound resilience according to JIS K6301 of 50% or more, and a thickness of 2 mm. 60% light transmittance
A polyurethane elastomer molded article as described above. It is in. Hereinafter, the present invention will be described in detail.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION

(1) Solution A (Prepolymer) The urethane prepolymer containing an NCO group at a terminal (hereinafter abbreviated as prepolymer) used as the solution A in the present invention is carbodiimide-modified diphenylmethane diisocyanate (hereinafter abbreviated as carbodiimide-modified MDI). And polytetramethylene ether glycol (hereinafter P
(Abbreviated as TMG). Carbodiimide-modified MDI refers to a carbodiimide compound (uretonimine) of 5 to 40% by weight, preferably 10 to 35% by weight.
Contains MDI. If the carbodiimide content is within the above range, a mixture of carbodiimide-modified MDI having a high carbodiimide content and 4,4′MDI may be used. When the content of the carbodiimide compound is less than 5% by weight, the improvement effect of lowering the mold temperature is small. On the other hand, when the content exceeds 40% by weight, the viscosity increases and the workability is increased. It is not good because it gets worse. The carbodiimide-modified MDI is commercially available, for example, as Isonate 143L (manufactured by Mitsubishi Chemical Dow).

Further, part of the carbodiimide-modified diphenylmethane diisocyanate can be replaced with another polyisocyanate compound as long as the workability and physical properties are not impaired. Other polyisocyanate compounds include, for example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, p-phenylene diisocyanate, tolidine diisocyanate, naphthalene-1,5-
Aromatic diisocyanate such as diisocyanate; aliphatic diisocyanate such as hexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, dimer acid diisocyanate, lysine methyl ester diisocyanate; isophorone diisocyanate;
Alicyclic diisocyanates such as 4,4-methylenebis (cyclohexyl isocyanate) and ω, ω'-diisocyanate dimethylcyclohexane; and aromatic rings such as xylene diisocyanate and m-α, α, α ', α'-tetramethyl xylylene diisocyanate Aliphatic diisocyanate.

[0010] PTMG used for the liquid A and the liquid B described later as required, may be other polyether polyols,
It is possible to give an elastomer cast product excellent in abrasion resistance, water resistance and high resilience, which cannot be obtained with a polyester polyol. PTMG having a number average molecular weight in the range of 650 to 4,000 can be used alone or in combination of two or more. Preferably, the number average molecular weight ranges from 650 to 3,000. If the number average molecular weight is less than 650, the rebound resilience decreases, and if the number average molecular weight exceeds 4,000, the crystallinity of the elastomer increases and the transparency decreases, which is not preferable.

Usually, P in the total weight of solution A and solution B
The TMG content is preferably set to be 50 to 85% by weight. If the content of PTMG is less than 50% by weight, cast products having a rebound of 50% or more cannot be obtained, and if the content exceeds 85% by weight, only cast products having insufficient hardness tend to be obtained. is there. PTMG is disclosed in, for example,
It can be produced by ring-opening polymerization of tetrahydrofuran as described in JP-A-162522.

The above molecular weight of PTMG is a number average molecular weight calculated from the amount of terminal hydroxyl groups. Solution A is MDI
Is set so that the molar ratio at the time of reacting the compound with PTMG is excessive in NCO groups and the NCO groups in the solution A are 3 to 15% by weight. If the content of the NCO group is less than 3% by weight, the viscosity of the solution A becomes high, and bubbles are difficult to be removed at the time of casting, and the workability is undesirably reduced. On the other hand, when the NCO group exceeds 15% by weight, it is difficult to control the reaction with the solution B, and it is easy to foam at the time of casting. The prepolymer of the liquid A is obtained, for example, by reacting the carbodiimide-modified MDI and PTMG under stirring in a dry nitrogen stream at 80 ° C. for 3 to 5 hours. A stabilizer can be added to the liquid A as needed. Examples of the stabilizer include an acidic phosphate ester type and a phosphite ester type. Acid phosphates include butyl acid phosphate, 2-ethylhexyl acid phosphate, indecyl acid phosphate, and the like, and phosphites include triphenyl phosphite,
Tridecyl phosphite, dibutyl hydrogen diene phosphite and the like can be mentioned.

(2) Liquid B (curing agent) The curing agent of liquid B comprises at least glycol containing 1,4-butanediol and neopentyl glycol, and a catalyst. As other glycol components, PTMG or the like may be used in combination, if necessary.

Neopentyl glycol The amount of neopentyl glycol to be used in the liquid B with respect to 1,4-butanediol is 1 to 70 mol%, preferably 10 to 70 mol%. If it is less than 1 mol%, the resulting molded article has high crystallinity and it is difficult to obtain a transparent molded article. On the other hand, if the used amount exceeds 70 mol%, it is not preferable because it is a cast product with lowered hardness and rebound resilience.

Catalyst As a catalyst used in the present invention, a catalyst used in a usual urethanization reaction is used. For example, tin compounds such as dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctoate, stannas octoate, dibutyltin diacetate, dibutyltin didodecyl mercaptide; iron compounds such as iron acetyl acetate and ferric chloride; Double salts of ethylenediamine, triethylamine and triethylenediamine; and tertiary amines such as tetramethylhexamethylenediamine. These catalysts may be used alone or in combination of two or more. Among them, dibutyltin dilaurate alone, triethylenediamine alone, or a combined catalyst using triethylenediamine and a triethylenediamine double salt is preferable. The amount of the catalyst to be added is 3 to 10,000 ppm by weight, preferably 5 to 5,000 ppm by weight in the total amount of the solution A and the solution B. If the amount is less than 3 ppm by weight, the demolding time is prolonged, and if it exceeds 10,000 ppm, the pot life after mixing of the reaction components (the solution A and the solution B) becomes too short, and neither is preferable.

Polytetramethylene ether glycol (PTMG) If necessary, PTMG used for the solution A is PTMG used for the solution A. In order to increase the crosslink density, a triol such as trimethylolpropane or glycerin can be optionally used in combination with neopentyl glycol.

Other components The liquid B of the present invention may contain a pigment, a plasticizer, a waterproofing agent,
Additives such as antioxidants, ultraviolet absorbers and light stabilizers can be added. As pigments, carbon black,
Examples of titanium oxide, red iron oxide, graphite, phthalocyanine-based organic pigments, and plasticizers include dibutyl phthalate and dioctyl phthalate.

(3) Mixing of liquid A and liquid B The method of preparing the composition of the present invention is based on various production methods generally used for castable elastomers, for example, a prepolymer method (liquid A is an NCO-terminated urethane prepolymer. B solution is a method of blending and using solution A and solution B which are chain extenders),
Semi-one-shot method (Solution A is composed of NCO-terminated prepolymer and MDI monomer and Solution B is composed of PTMG and a chain extender.
Liquid and liquid B).

The equivalent ratio of NCO group / OH group in solution A and solution B is 0.90 to 1.20, preferably 0.98 to 1.20.
1.10. If it is less than 0.90, the physical properties are significantly reduced, and the curing properties are also reduced. On the other hand, when it exceeds 1.20, problems such as foaming at the time of casting occur. Further, the liquid temperature at the time of mixing the liquid A and the liquid B is determined in consideration of the viscosity and the reactivity, and is usually preferably 20 to 100 ° C.

(4) Casting When casting the urethane elastomer composition for casting of the present invention using a mold, the temperature of the mold is preferably 50 to 100 ° C. in order to obtain a transparent molded product. Although a transparent molded article can be obtained even at 100 to 150 ° C., when a plastic mold is used, there is a problem such as deformation of the mold and energy cost is also required. If the mold temperature is lower than 50 ° C., it is difficult to obtain a transparent molded product. On the other hand, when the temperature is higher than 150 ° C., coloring occurs due to thermal deterioration, and neither is preferable.

[0021]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples unless it exceeds the gist. The reaction components used in the following examples are as follows. Unless otherwise specified, “parts” and “%” are based on weight. Production of Liquid A Production Examples 1 to 5 Production of Liquid A was performed by the following method. In a 1-liter glass flask, the carbodiimide-modified diphenylmethane diisocyanate (manufactured by Mitsubishi Chemical Dow: Isonate 143L (H type) (NCO
Group content 29%, carbodiimide compound content 25%), I
sonate 143L (M type) (NCO group content 27.7%, carbodiimide body content 30.5%)),
MDI (Mitsubishi Chemical Dow: Isonate 125M
(NCO group content: 33.6%) and various PTMGs (manufactured by Mitsubishi Chemical Corporation) were charged, mixed, and reacted at 80 ° C. for 5 hours under a nitrogen stream to obtain each prepolymer. Table 1 shows the measurement results of these compositions and the NCO content and viscosity of the obtained prepolymer. In addition, PTMG100 used for solution A
The number average molecular weights of 0 and 2000 are 1018 and 1018, respectively.
1958. The method for measuring the viscosity is as follows. The viscosity of the obtained resin solution was measured using an E-type viscometer (VI
SCONIC EHD-R type, manufactured by Tokyo Keiki Co., Ltd.). The measurement was performed at a measurement temperature of 30 ° C., a sample amount of 1.5 ml, and a standard rotor (1 ° 34 ′).

[0022]

[Table 1]

Production of Polyol for Liquid B Production Examples 6 to 14 Production of Liquid B was carried out by the following method. Each raw material in the number shown in Table 2 was charged into a glass flask having a capacity of 1 liter and uniformly mixed to produce a polyol for liquid B. The number average molecular weights of PTMG1000 and 2000 used were 1013 and 1945, respectively.

[0024]

[Table 2]

Examples 1 to 6 and Comparative Examples 1 to 4 Polyurethane elastomers were produced in the following manner in accordance with the formulation shown in Table 3. (Elastomer casting) Liquid A obtained in Production Examples 1 to 5 and Liquid B polyol obtained in Production Examples 6 to 14 (Table-3
At a predetermined temperature (40 to 90 ° C. for solution A)
B solution (20 to 60 ° C), vacuum defoaming, mixing, injection into a mold (55 mmφ × 13 mm thick) heated to a predetermined temperature (50 to 100 ° C) previously coated with a release agent, After curing for a time, a molded product was obtained. After aging the obtained elastomer molded product for 7 days (23 ° C., relative humidity (RH) 60%), physical properties were measured in accordance with JIS standards (JIS-K6301). The results are shown in Table-3. Table 4 shows the mechanical properties.

As a mold, a sheet molding mold (20)
A 2 mm thick sheet was prepared as a sample for evaluation of transparency by the same manufacturing method as in the preparation of the above-mentioned elastomer molded product except that 0 mm × 200 mm × 2 mm thickness was used. In addition,
The transparency of the elastomer molded article was evaluated as ○ when the light transmittance (T) in a 2 mm thick sheet was 60% or more, and as X when less than 10%.

[0027]

[Table 3]

[0028]

[Table 4]

[0029]

[Table 5]

[0030]

The polyurethane elastomer composition for casting according to the present invention has a composition of 50 to 1 which cannot be realized with conventional products.
JIS while being fast-curing at a mold temperature of 00 ° C
A hardness in K6301 is 70 or more, and
A transparent polyurethane elastomer molded article having a rebound resilience of 50% or more can be provided. In addition, since casting can be performed at a low temperature, an inexpensive metal mold such as plastic can be used.

Claims (5)

[Claims] 1. A solution containing an isocyanate group-terminated urethane prepolymer obtained by reacting carbodiimide-modified diphenylmethane diisocyanate with polytetramethylene ether glycol, and a B solution containing 1,4-butanediol and neopentyl glycol. And a curing agent containing a catalyst, wherein the ratio of neopentyl glycol to 1,4-butanediol is 1 to 70 mol% in the liquid B. Polyurethane-based elastomer composition. 2. The polyurethane elastomer composition for casting according to claim 1, wherein polytetramethylene ether glycol is further blended with Liquid B. 3. A carbodiimide-modified diphenylmethane diisocyanate is a carbodiimide (uretonimine)
The polyurethane elastomer composition for casting according to claim 1 or 2, which is a diphenylmethane diisocyanate containing 5 to 40% by weight of 4. The composition according to claim 1, wherein the composition is cast at a mold temperature of 100 ° C. or less, and then cured to obtain a light transmittance of 60 mm at a thickness of 2 mm.
% Polyurethane molded article. 5. A JI obtained by casting the composition according to claim 1 and then curing it.
Hardness according to SK6301 (A standard) is 70 or more,
The rebound resilience based on JIS K6301 is 50% or more,
A polyurethane elastomer molded article having a light transmittance of 60% or more at a thickness of 2 mm.