JPH11310624A - Production of polyurethane foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyurethane foam retaining sufficient strength even in a low density by reacting a polyol component with a polyisocyanate compound in the presence of water and a specific amount of urea. SOLUTION: (A) A polyol component [e.g. a polyoxypropylene-based polyol (PPG) having >=1,500 molecular weight per hydroxyl group obtained by adding ethylene oxide to the terminal hydroxyl group of a polyoxypropylenepolyol, etc.], is reacted with (B) a polyisocyanate compound (e.g. tolylene diisocyanate or the like) in the presence of (C) a catalyst (e.g. 1,2-dimethylimidazole or the like), (D) water and (E) 0.1-0.9 pt.wt. based on 100 pts.wt. of the component A of urea. In the reaction, the ratio of the component A to the component B is preferably adjusted to give 90-110 isocyanate index. The amount of the component C used is preferably 0.1-1.8 pts.wt. based on 100 pts.wt. of the component A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a polyurethane foam, and more particularly to a method for producing a polyurethane foam for shoe soles.

[0002]

2. Description of the Related Art Polyether polyurethane is superior in hydrolysis resistance to polyester polyurethane, and is preferably used for men's shoes used for a long time.
Since mechanical properties such as abrasion resistance and room temperature flexibility are inferior, it is desired to achieve both.

[0003] In order to improve the mechanical properties and the like of the polyether-based polyurethane, it has been proposed to replace all or part of the polyoxypropylene-based polyol with polyol tetramethylene glycol as a polyol component. However, in general, polyether-based polyurethane has poor mechanical properties, and particularly in low-density soles, the final strength as a product as well as at the time of foam molding is insufficient, and it is difficult to commercialize the product.

Japanese Unexamined Patent Publication (Kokai) No. 61-268716 discloses that a low-molecular-weight polyol and a high-molecular-weight polyol are used in combination, and 1 part by weight or more of urea and 2 parts by weight or more of water are used per 100 parts by weight of a polyol, to provide air permeability. And a method for producing a non-flexible polyurethane foam having excellent dimensional stability. However, there is no suggestion about a method for improving the strength of a polyurethane foam by using a specific amount of urea.

Japanese Patent Application Laid-Open No. 60-84355 discloses that a mixture of a low-molecular-weight polyol and a high-molecular-weight polyol, which are usually incompatible, is mixed at 25 ° C. without gelling the mixture.
Discloses a method for producing a polyurethane using the resulting compatible mixture in combination with an amount of urea or a derivative thereof sufficient to maintain the composition in a single liquid phase for at least 5 days. However, the resulting urethane is not a foam, and urea is merely used as a compatibilizer, and there is no suggestion about a method for improving the strength of the polyurethane foam by using a specific amount of urea. Absent.

[0006] JP-T 4-502926 discloses that in the production of an improved flame-retardant polyurethane foam, urea is dissolved in a mixture of a polyether polyol or a polyester polyol and a sugar such as sucrose or lactose. From about 5% by weight to about 15% by alkoxylation of the resulting product with an alkylene oxide.
It discloses that an alkoxylated polyol containing urea by weight is used. However, the amount of urea used is relatively large, and there is no suggestion about a method for improving the strength of the polyurethane foam by using a specific amount of urea.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a polyurethane foam having a sufficient strength even at a low density. In particular, the present invention suitably provides a method for producing a polyurethane foam for shoe soles.

[0008]

That is, the present invention provides a polyol component and a polyisocyanate compound, which are used in an amount of 0.1 to 0.1 parts by weight based on 100 parts by weight of a catalyst, water and a polyol component.
The present invention relates to a method for producing a polyurethane foam, which comprises reacting in the presence of 9 parts by weight of urea.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the polyol component include polyether polyols having two or more hydroxyl groups (hereinafter referred to as polyether polyols) and polymer polyols based on polyether polyols (hereinafter referred to as polymer polyols). .

Representative examples of the polyether polyols include polyoxypropylene-based polyols (hereinafter referred to as PPG) having a molecular weight of 1500 or more per hydroxyl group obtained by adding ethylene oxide to terminal hydroxyl groups of polyoxypropylene polyol, and tetrahydrofuran. Examples include polyoxytetramethylene glycol (hereinafter referred to as PTMG) having a molecular weight of 1000 or more obtained by ring-opening polymerization and a mixture thereof.

Since the above PPG has a long repetition of oxypropylene chains, it works effectively as a soft segment in the obtained polyurethane foam and plays a role of improving elongation characteristics and bending characteristics. Therefore, PPG is preferably used in the present invention. It is a good thing. In the PPG, the molecular weight per hydroxyl group is preferably 1 to make the role of the oxypropylene chain as a soft segment effective.
It is 500 or more, more preferably 1800 or more. The upper limit of the molecular weight is preferably 2 from the viewpoint of viscosity during handling.
0000 or less, more preferably 10,000 or less.

The PPG is produced by using a compound having two or more active hydrogens as a starting material, subjecting the compound to a conventional ring-opening addition reaction of an alkylene oxide, and further adding ethylene oxide to the molecular terminal in a block manner. be able to.

As the starting materials, polyhydric alcohols,
Examples include polyhydric phenols, polyamines, alkanolamines, and the like. Specific examples include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, glycerin, trimethylolpropane, pentaerythritol,
Examples thereof include diglycerin, dextrose, sucrose, bisphenol A, ethylenediamine, and their modified products, and these can be used alone or in combination of two or more.

Examples of the alkylene oxide to be subjected to the ring-opening addition reaction to the starting materials include ethylene oxide, propylene oxide, 1,2-butylene oxide, 2,3
-Butylene oxide, styrene oxide and the like. Among these, propylene oxide is used alone, or propylene oxide is used as a main component (50% by weight or more) and is used in combination with another alkylene oxide so as to form a random copolymer or a block copolymer. Is preferred.

After the reaction between the starting material and the alkylene oxide, a blockwise addition reaction of ethylene oxide is carried out so that the terminal hydroxyl group becomes primary in order to increase the urethane-forming reactivity in producing a polyurethane foam. Is preferred. The primary hydroxylation ratio of terminal hydroxyl groups by ethylene oxide (the number of primary hydroxyl groups / the total number of hydroxyl groups) increases the urethane-forming reactivity when producing a polyurethane foam,
From the viewpoint of shortening the demolding time and improving the balance between the resinification rate and the foaming rate so as not to cause shrinkage in the polyurethane foam, it is preferably at least 50%, more preferably at least 80%. preferable.

By the way, when the content of oxyethylene groups present inside and at the terminal of PPG is increased, hydrophilicity is increased and water is attracted, so that hydrolysis resistance, which is a characteristic of polyether-based polyurethane foam, is reduced. Therefore, the content of oxyethylene groups in the PPG is 3
The content of the oxyethylene group in the PPG is preferably 5% or more from the viewpoint of the primary conversion rate of the terminal hydroxyl group. In addition, the PPG
Is prepared by mixing several kinds of polyoxyalkylene polyols as long as the molecular weight per hydroxyl group as a whole polyether polyol, the content of oxyethylene groups and the primary hydroxylation rate of terminal hydroxyl groups are within the above ranges. Is also good.

The PTMG has a property of improving mechanical properties such as strength from its molecular structure. The molecular weight of the PTMG is preferably 1,000 or more, more preferably 1400 or more, from the viewpoint of usefulness as a soft segment of the oxytetramethylene chain. The upper limit of the molecular weight is
From the viewpoint of maintaining the liquidity at the handling operation temperature, it is preferably 3000 or less, more preferably 2300 or less.

Typical examples of the polymer polyol include those in which polymer fine particles obtained by polymerizing a polymerizable unsaturated group-containing monomer are dispersed in a polyether polyol. This, for example,
A method of mixing and dispersing polymer fine particles obtained by polymerizing a polymerizable unsaturated monomer and a polyether polyol, by polymerizing the polymerizable unsaturated group-containing monomer in the polyether polyol, It can be produced by, for example, a method of dispersing polymer fine particles obtained from an unsaturated group-containing monomer in the polyether polyol. Among these methods,
The latter method is preferable because a polymer polyol in which polymer fine particles are uniformly dispersed in the polyether polyol can be easily obtained.

Examples of the polymerizable unsaturated group-containing monomer include styrene; acrylonitrile; alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms such as methyl methacrylate, ethyl methacrylate, and butyl methacrylate; glycidyl methacrylate;
Examples thereof include an alkyl acrylate having an alkyl group having 1 to 4 carbon atoms, such as ethyl acrylate and butyl acrylate; and glycidyl acrylate. These monomers can be used alone or in combination of two or more.

The above-mentioned PTMG is used as a polyol component.
Mechanical properties such as strength are synergistically improved by the combined use with the polymer polyol and 0.15 to 0.5 g / cm
It is possible to obtain a polyurethane foam having mechanical properties that can be sufficiently used for applications such as low-density soles of about 3.

The polyisocyanate compound used in the present invention includes aromatic, alicyclic, and aliphatic polyisocyanates having two or more isocyanate groups, mixtures thereof, and modified polyisocyanates obtained by modifying them. And isocyanate. Specific examples include tolylene diisocyanate, methylene diphenyl diisocyanate, naphthylene diisocyanate, xylylene diisocyanate, aromatic polyisocyanates such as polymethylene polyphenylene isocyanate, hydrogenated methylene diphenyl diisocyanate, hydrogenated tolylene diisocyanate,
Examples include alicyclic polyisocyanates such as isophorone diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate and lysine diisocyanate, mixtures thereof, and modified products thereof. Examples of the modified product include a prepolymer-based modified product, a nurate modified product, a urea modified product, a carbodiimide modified product, an allophanate modified product, and a buret modified product that are reaction products with a polyol. Of these, aromatic polyisocyanates and modified products thereof are preferred.

In particular, a modified prepolymer comprising polyoxyalkylene glycol and methylene diphenyl diisocyanate and / or a modified product thereof has a structure containing a soft segment composed of polyoxyalkylene glycol, and has a low density polyurethane foam. It is particularly effective for improving characteristics.

The polyoxyalkylene glycol is
The PPG can be manufactured by the same method as that for preparing the PPG. Among polyoxyalkylene glycols, a polyoxypropylene glycol having a molecular weight per hydroxyl group of 1000 or more can be suitably used, and since the oxyalkylene chain repeat is long, the soft segment in urethane foam is used. Works effectively, and elongation and bending characteristics are improved. Since the polyoxyalkylene glycol reacts with the polyisocyanate in advance, it is not always necessary to primaryize the hydroxyl group, and ethylene oxide may be added to the terminal or may not be added. The modified prepolymer may contain a reaction product of methylene diphenyl diisocyanate or a modified product thereof and a crosslinking agent.

In the present invention, it is preferable to use a catalyst from the viewpoint of improving the reaction rate. Tertiary amines are preferred as catalysts.

Specific examples of the catalyst include, for example, TE
DA [1,4-diazabicyclo- (2,2,2) -octane], N, N, N ', N'-tetramethylhexamethylenediamine, N, N, N', N'-tetramethylpropylenediamine, N, N, N ', N', N "-pentamethyldiethylenetriamine, trimethylaminoethylpiperazine, N, N-dimethylcyclohexylamine, N, N-dimethylbenzylamine, N-methylmorpholine, N-ethylmorpholine, triethylamine, tributylamine , Bis (dimethylaminoalkyl) piperazine, N, N, N ', N'-tetramethylethylenediamine, N, N-diethylbenzylamine, bis (N, N-diethylaminoethyl) adipate,
N, N ′, N′-tetramethyl-1,3-butanediamine, N, N-dimethyl-β-phenylethylamine,
Examples thereof include 1,2-dimethylimidazole and 2-methylimidazole, and these catalysts may be used alone.
Further, two or more kinds may be used as a mixture. In the present invention, as a catalyst other than the tertiary amine, an organic metal compound such as dibutyltin dilaurate, stannous oleate, cobalt naphthenate, or lead naphthenate may be used.

As the foaming agent used in the present invention, water is an essential component, and hydrocarbons, chlorofluorocarbons, hydrogenated fluorocarbons and the like may coexist. From the viewpoint of avoiding the problem of ozone depletion on the earth, it is preferable to use water alone. When only water is used as the foaming agent, the water content is 0.1 to 100 parts by weight of the polyol component.
The amount is preferably from 1 to 1.8 parts by weight, particularly preferably from 0.3 to 1.5 parts by weight.

In the present invention, silicone-based foam stabilizers, crosslinking agents, pigments, antioxidants, yellowing inhibitors and the like can be used as additives.

Examples of the crosslinking agent include low molecular weight compounds having two or more active hydrogen-containing groups capable of reacting with a hydroxyl group, a primary amino group, a secondary amino group, and other isocyanate groups. Specific examples include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, glycerin, trimethylolpropane, triethanolamine, and alkylene oxides of bisphenol A. Examples thereof include polyhydric alcohols such as adducts, and polyamines such as diethyltoluenediamine, chlorodiaminobenzene, ethylenediamine, and 1,6-hexanediamine. However, the present invention is not limited to such examples. In the present invention,
The crosslinking agents can be used alone or in combination of two or more.

In the present invention, when the polyol component is reacted with the polyisocyanate compound, the ratio of the two is preferably adjusted so that the isocyanate index is 90 to 110, and more preferably 95 to 110.
5, particularly preferably 99 to 101.

The urea used in the present invention has the chemical formula N
H2CONH2, wherein the amount of urea used is 0.1 to 0.9 parts by weight with respect to 100 parts by weight of a polyol component from the viewpoint of obtaining high strength;
It is preferable to mix by weight, and particularly preferable to be 0.4 to 0.7 weight part. If the amount is less than 0.1 part by weight, the effect of improving the strength is not recognized. If the amount exceeds 0.9 part by weight, urea adversely affects the improvement in strength, and sufficient strength cannot be obtained during foam molding.

In the present invention, especially in a system containing PPG, the use of an optimal amount of urea improves the strength of the polyurethane foam obtained when compared with the same isocyanate index, and reduces the cost of PP.
Even if G is used, a sufficient improvement in the initial strength is recognized, and there is an advantage that the demolding time can be shortened.

Further, in systems containing PPG, the isocyanate index of 90 to 95
It has been commercialized by foaming with a polyol excess system, but by adding urea, sufficient initial strength can be expressed and molding with an isocyanate index of 100, which is said to have the best final physical properties, is possible. Becomes This means that a polyurethane foam having improved initial and final physical properties can be obtained, and is particularly suitable for a polyurethane foam for shoe soles.

In the present invention, the effect of urea is remarkable when the content of PPG in the polyol component is 20% by weight or more, and particularly remarkable when the content is 50% by weight or more. Reducing the content of expensive PTMG and increasing the content of inexpensive PPG is provided by the addition of urea,
It is economically important from the viewpoint of producing inexpensive polyurethane foam.

In the present invention, the urea addition effect is remarkable when the isocyanate index is 95 to 105.

As a method for producing the polyurethane foam of the present invention, for example, a polyol, a catalyst, a blowing agent, urea and other additives are mixed and stirred in advance, and a polyisocyanate compound is mixed and stirred by a molding machine. And a method of injecting into a mold and foaming. More specifically, for example, after mixing and stirring the polyol component using a tank or the like, and usually adjusting the temperature to about 40 ° C., foaming such as an automatic mixing injection type foaming machine and an automatic mixing type injection foaming machine. And foaming with a polyisocyanate compound using a mixer.

[0036]

【Example】

Examples 1 to 12 and Comparative Examples 1 to 13 As the polyether polyol and the polymer polyol, the compounds shown in Tables 1 to 3 were used, and the proportions were adjusted as shown in Tables 1 to 3. The amount of each component is 100% of the total of the polyol components (hereinafter abbreviated as polyol component).
Expressed in parts by weight relative to parts by weight.

Per 100 parts by weight of the polyol component, a predetermined amount of ethylene glycol as a crosslinking agent, a predetermined amount of a polyalkylsiloxane as a foam stabilizer (trade name: SRX253, manufactured by Dow Corning Silicone Toray Co., Ltd.), and a catalyst Quantitative TEDA [1,4-diazabicyclo-
(2,2,2) -octane], a predetermined amount of water, and a predetermined amount of urea were added and stirred to prepare a polyol solution containing a polyol component of a foaming machine. The appearance of the polyol solution was a pale yellow opaque liquid at 25 ° C., and the phases separated over time.

As a polyisocyanate compound, a polyol-modified diphenylmethane diisocyanate [Kao Corporation]
Product name: Eddy Form B-6106M, NCO
%: 16%].

The mixing ratio of the polyol solution and the polyisocyanate compound is determined in consideration of the free-form state in the foaming reaction, and [(actually used isocyanate amount) / (stoichiometrically equivalent to the polyol). Isocyanate index)] × 100 was about 90 to 110. Tables 1 to 3 show specific amounts of polyisocyanate compounds in parts by weight based on 100 parts by weight of the polyol solution.

A polyol solution having the compounding ratio shown in Tables 1 to 3 was placed in one tank of a low-pressure foaming machine of the pore type, the temperature of the solution was adjusted to 35 to 45 ° C., and the polyisocyanate compound was placed in the other tank. And adjust the solution temperature to 3
5-45 ° C. Using the foaming machine, the polyol solution and the polyisocyanate compound are mixed and stirred, injected into a mold and foamed, and 100 mm × 300 mm × 10
mm of polyurethane foam was obtained.

The foam properties of the obtained polyurethane foam were examined according to the following methods. Tables 1-3 show the results.
Shown in

The abbreviations of the polyol components used in the examples and comparative examples mean the following. [Polyether polyol] <PPG> Polyether polyol 1: Polyoxyethylene-terminated polyoxypropylene triol having a molecular weight of 7000 in which propylene oxide and ethylene oxide are sequentially added to a trifunctional alcohol [trade name: Exenol, manufactured by Asahi Ohlin Co., Ltd.] 850] <PTMG> Polyether polyol 2: Polyoxytetramethylene glycol having a molecular weight of 2000 [Hodogaya Chemical Industry Co., Ltd.
Manufactured and trade name: PTG-2000SNW] [Polymer polyol] Polymer polyol 1: Obtained by polymerizing acrylonitrile / styrene in polyoxyethylene-terminated polyoxypropylene triol obtained by sequentially adding propylene oxide and ethylene oxide to a trifunctional alcohol. Polyol containing fine particles [manufactured by Asahi Ohlin Co., Ltd., trade name: Exenol 941]

1. Demolding test was performed according to the following method. A predetermined aluminum mold is heated to 50 ° C. The raw material is injected into the mold so as to have the target density, and then sealed. For a certain period of time (4.5 minutes or
After 6.5 minutes), the mold is opened and the molded product is released. At the time of demolding, the user puts his hand on the longitudinal end of the molded product and pulls it out at once. Observe the appearance of the notch near the center in the long axis direction of the molded product. "A" indicates that there is no abnormality in the appearance, "O" indicates that a fine crack is observed but there is no practical problem, and "X" indicates that a clear crack is formed.

2. Foam characteristics (molding density) The weight of a polyurethane foam of 100 mm x 300 mm x 10 mm was measured, and the volume was 300 cm3.
Divided by. (Hardness) It was measured with an Asker C hardness meter. (Initial tensile strength and initial elongation) Measured according to the following methods. After injecting the raw material into a mold at 50 ° C., the mold is released 5 minutes later. A sample is punched out with a predetermined dumbbell and integrated after starting injection of the raw material, and after 7 minutes, the initial tensile strength and initial elongation are measured according to JIS K-6301. (Tensile strength) According to JIS K-6301. (Elongation) According to JIS K-6301.

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

[Table 3]

From the results shown in Tables 1-3, Examples 1 to
The polyurethane foam obtained in No. 12 was subjected to a demolding test to determine that the amount of the polyurethane foam was 0.1 to 0.1 with respect to 100 parts by weight of the polyol component.
By adding 9 parts by weight of urea, a molded article having practically no problem in appearance can be obtained. The effect is large when the amount of urea is 0.1 to 0.6 parts by weight with respect to the polyol component. You can see that.

The polyurethane foams obtained in Comparative Examples 2, 3, 5, 6 and 13 have a serious disadvantage that, unlike Examples 1 to 7, the amount of urea is out of the range of the present invention and cannot be removed from the mold. . Also, Examples 2 to 6 and Comparative Examples 1 to
From the comparison of Comparative Example 3 and Comparative Examples 4 to 6, improvement in the initial tensile strength by adding the amount of urea of the present invention was clearly recognized. On the other hand, from the comparison of Examples 2 to 6 and Comparative Examples 4 to 6,
It is shown that when the added amount of urea exceeds the range of the present invention, the tensile strength decreases.

Example 8 is compared to Comparative Example 9 and Comparative Example 1
As shown in Example 9 with respect to 0, in the system containing PPG, the improvement of the strength of the polyurethane foam by adding an amount of urea within the range of the present invention is remarkable.

As is clear from Example 10 and Comparative Example 11, the PTMG system has a high level of strength even without urea, and is not as remarkable as the PPG system. The effect of improving the strength by performing was confirmed.

Focusing on the index 100, as apparent from Example 4 and Comparative Examples 2 and 5, P
In the case of the PG system, improvement in the initial tensile strength was observed by adding the amount of urea within the range of the present invention, and demolding was possible. As is clear from Example 12 and Comparative Example 13, in the polymer polyol system, the initial strength was improved by adding urea, and demolding was possible.

A description will be given focusing on the index 90.
Originally, this system has strong initial strength and can be demolded,
Example 2 and Comparative Examples 1 and 4 and Example 11 and Comparative Example 1
As is clear from FIG. 2, further improvement in the initial tensile strength was observed.

When the isocyanate index was 100 and the urea content was changed in a PPG-containing system containing no PTMG, the tensile strength was found to be the highest when the urea content was 0.6 parts by weight, as compared with Examples 1, 4 and 7. Became higher.

As shown in Comparative Examples 7 and 8, in a system without addition of water, the effect of the addition of urea within the range of the present invention was not recognized at all, whereas in Examples 1, 4 and 7 In addition, as shown in Comparative Examples 2 and 5, in a system with addition of water, the effect of the addition of urea within the range of the present invention is remarkable in that demolding becomes possible.

[0057]

According to the present invention, the polyol component 100
By adding 0.1 to 0.9 parts by weight of urea to parts by weight, it is possible to remove the mold, and to produce a polyurethane foam having sufficient initial strength at the time of foam molding and final strength as a product. Can be.

In a system containing PPG, the initial strength can be improved by adding 0.1 to 0.9 parts by weight of urea to 100 parts by weight of the polyol component. In particular, when compared with the same isocyanate index, improvement in the initial strength is apparent, which leads to improvement in productivity.

The system containing PPG has an isocyanate index of 90 to 95 in order to emphasize productivity.
However, by adding 0.1 to 0.9 parts by weight of urea to 100 parts by weight of the polyol component, the final physical properties are improved with an isocyanate index of 100. It develops initial strength and enables molding with an isocyanate index of 100.

Claims (3)

[Claims] 1. A method for producing a polyurethane foam, comprising reacting a polyol component with a polyisocyanate compound in the presence of 0.1 to 0.9 parts by weight of urea based on 100 parts by weight of a catalyst, water and the polyol component. 2. The method for producing a polyurethane foam according to claim 1, wherein a polyoxypropylene-based polyol is used as at least one of the polyol raw materials constituting the polyol component and the polyisocyanate compound. 3. The method for producing a polyurethane foam according to claim 2, wherein the polyisocyanate compound has an isocyanate index of 90 to 110.