JPS6047038A - Polyurethane sheet material of low discoloration - Google Patents

Abstract

PURPOSE:To obtain a sheet material of low discoloration, by applying a solution of a specified polyurethane elastomer to a base and forming it into a film of a porous structure by a wet coagulation process. CONSTITUTION:The following polyurethane elastomer solution is applied to a base and formed into a film of a porous structure by a wet coagulation process to form a sheet meterial. Said polyurethane elastomer is one obtained by reacting a polyol with 70-95mol%, based on the polyol, diphenylmethane 4,4'-diisocyanate and reacting the product with 5-30mol%, based on the polyol, nonaromatic diisocyanate. The porous structure of this sheet material is formed in such a way that the solvent of the polyurethane elastomer solution is dissolved in a coagulant during coagulation, the places are filled with the coagulant and the whole is coagulated while the places survive as pores. The size of a cell at this time can be varied freely by selecting the resin concentration of a solution, the composition of a coagulant, a coagulation bath temperature, and a coagulation aid, and a size of a cell of about 10-1,000mu is adopted.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sheet material having a porous structure produced by wet coagulation of a polyurethane elastomer and exhibiting little discoloration.

General polyurethane sheet materials obtained using the wet coagulation method have excellent properties as a substitute for leather, but their use is limited because they tend to discolor to yellow or brown when exposed to sunlight or nitrogen oxide gas. ing. For this purpose, methods of adding ultraviolet absorbers, antioxidants, etc. are known, but while this is effective in the dry method, in the case of the wet method, the added ultraviolet absorbers and antioxidants are added to the coagulation bath. It has the disadvantage that it hardly shows any effect because it is eluted and does not remain in the sheet material.

On the other hand, so-called non-yellowing urethanes using non-aromatic diisocyanates have extremely excellent resistance to discoloration, but have poor physical properties such as heat resistance and bending resistance. Non-aromatic diisocyanates are not commonly used because they are very expensive and have poor M-film properties. Polyurethanes have also been proposed in which non-aromatic diisocyanates are mixed with aromatic diisocyanates.
It is necessary to contain 0 mol% or more, in that case,
It cannot be put to practical use because of its poor heat resistance and poor wet film-forming properties.

The present inventors have conducted intensive research into various methods to improve the drawbacks of the above-mentioned conventional techniques and prevent discoloration of polyurethane sheet materials due to sunlight, nitrogen oxide gas, etc., and as a result, they have arrived at the present invention.

That is, in the present invention, a polyurethane elastomer solution obtained by reacting 70 to 95 mol% of diphenylmethane-4,4'-diisocyanate with a polyol and then reacting with a non-aromatic diisocyanate is coated on a substrate. The present invention provides a polyurethane sheet material with little discoloration, which is formed into a porous structure by a wet coagulation method.

Among the raw materials for the polyurethane elastomer used in the present invention, aliphatic polyols are preferred as polyols, and polyester polyols having a molecular weight of 500 to 5,000 or polyether polyols having a molecular weight of 600 to 3,000 are preferably used as polyols. Molecular weight diol and low molecular weight diol with a molecular weight of 60 to 250 and/or
Alternatively, it can be used in combination with diamine. Examples of polyester polyols include succinic acid, adipic acid,
Aliphatic dibasic acids such as sebacic acid and ethylene glycol, propylene glycol, diethylene glycol, butane-1,3-diol, butane-1,4-diol,
Polyester polyols obtained by reacting with glycols such as 2,2-dimethylpropane-1°3-diol and hexane-1,6-diol are preferred. or,
Polyesters of diphenyl carbonate and the aforementioned glycols and polyesters obtained by ring-opening polymerization of caprolactone are also suitable.

Examples of the polyether include polypropylene ether glycol and volite 1-ramethylene ether glycol.

Low molecular weight diols and/or diamines include ethylene glycol, butane-1,4-diol, hexane-
1°6-diol, 4,4'-diphenylmethanediamine, ethylenediamine and the like are preferred.

As the non-aromatic diisocyanate, those having a symmetrical structure such as hexane-1°6-diisocyanate, cyclohexane-1,4-diisocyanate, and dicyclohexylmethane-4,4'-diisocyanate are suitable.

The reaction of these polyols with diphenylmethane-4,4'-diisocyanate and the subsequent reaction with non-aromatic diisocyanate are carried out in a solvent-free system at 50°C to 200°C.
, 1 minute to 120 minutes, or 30℃ to 100℃ in a solvent
, continuous type for 30 minutes to 10 hours! Either Kutsuchi style is acceptable. Further, as a solvent for dissolving the polyurethane elastomer, a water-soluble and highly polar solvent such as N,
N-dimethylformamide, N,N-dimethylacetamide and the like are preferably used.

The method for coagulating the polyurethane elastomer solution is not particularly limited, but usually involves immersing the polyurethane elastomer solution in a coagulating solution that is a poor solvent for the polyurethane elastomer and has an affinity for the solvent of the solution. However, this is a method of coagulating polyurethane elastomer, and a wet coagulation method is used that utilizes pores created when a solvent is eluted into a coagulating liquid. For example, T1. l
coating method, and (2) impregnation method.The coating method involves applying a resin solution with a solid content concentration of 8 to 30% to a thickness of 50%.
0-1500 gr/Apply with knife, roll, etc., 1
Water at 5-50℃/DMF = 100/(1-70/30
immersed in a coagulation bath consisting of
This is a method to obtain a sheet by drying for minutes. In addition, the impregnation method is
After immersing the base fabric in a polymer solution with a solid content concentration of 5 to 20%, use a squeezing roll (the clearance is 1/3 to 2 of the thickness of the base fabric).
/3) After squeezing, coagulation, washing, and drying are performed in the same way as the coating method. The base material is natural fiber such as cotton,
Nylon, polyethylene terephthalate, vinylon, acrylic, polyester, etc. Synthetic tJ-fiber webs, woven fabrics, non-woven fabrics, etc. In addition to substrates to which the polymer/8 solution is directly coated or impregnated, wet films were formed on polyethylene terephthalate films. After that, there is also a method of laminating the above-mentioned woven fabric, non-woven fabric, etc.

As mentioned above, the porous (11) structure of the present invention is produced when the solvent of the polyurethane elastomer melt dissolves into the coagulating liquid, and then the coagulating liquid enters and coagulates in a porous state. be. Does the size of the bubbles at this time depend on the resin concentration of the solution and solidification? The thickness can be arbitrarily changed depending on Pj, W composition, coagulation bath temperature, and coagulation aid, and is about 10 to 1000 μm.

In the solution of polyurethane elastomer, various additives such as pigments, surfactants, and stabilizers, and various polymers such as cellulose aceto-1, polyvinylpyrrolidone, and acrylonitrile-styrene copolymer can be mixed and used. can.

As mentioned above, the polyurethane elastomer used in the present invention is initially 70 to 95 mol% based on the polyol.
Diphenylmethane-4,4' to diisocyanate I are reacted to synthesize an active hydrogen-terminated urethane prepolymer, and then reacted with 5 to 30 mol% of a non-aromatic diisocyanate to obtain an elastomer. ,
In this case, if the amount of diphenylmethane-4,41-diisocyanate is less than 70 mol% of the polyol, wet coagulation will be significantly slowed down, whereas if it is more than 95 mol%, the effect of preventing discoloration will be lost, which is not preferable. In addition, the discoloration of sheet materials made using polyurethane elastomers obtained by changing the reaction order and first reacting a non-aromatic diisocyanate with a polyol and then reacting diphenylmethane-4,4'-diisocyanate was caused by diphenylmethane. −
4,4'-diisocyanate-1 was as bad as when used alone, and furthermore, when the wet coagulation number J was lowered, non-aromatic diisocyanate and diphenylmethane-1
Even when 4,4'-diisocyanate is simultaneously reacted with polyol, wet coagulation is significantly delayed and the anti-discoloration effect is also reduced.

As described above, by employing the method of the present invention, the unique effect of preventing discoloration while maintaining the excellent wet film forming properties of diphenylmethane-4,4'-diisocyanate is achieved. be.

This LW mountain is caused by aromatic urethane at the end of the molecule of the urethane elastomer designed by the method of the present invention, whereas general urethane elastomer is easily decomposed at the end by energy such as sunlight. Decomposes due to the presence of non-aromatic urethane bonds that have a higher bonding strength than 3! This is because even if it is further decomposed, it does not form a chromophore, making discoloration less likely to occur. Moreover, the urethane elastomer of the present invention maintains its crystallinity as it does not contain non-aromatic urethane bonds in the main part, and has the unique effect of having extremely excellent wet film formability.
become what is done.

The polyurethane sheet material of the present invention has a nitrogen oxide gas resistance of 1! ! : It can be used in many fields such as footwear such as shoes, bags, and clothing.

Next, examples of the present invention will be shown, in which parts and percentages are based on the T[R'l- standard unless otherwise specified.

Example 1 Four four-eye flasks A and B equipped with stirrer and thermometer.

Polytetramethylene adipate with a molecular weight of 2000 ft, ethylene glycol and N, N in the proportions shown in Table 1 for C and D.
- Dimethylformamide (hereinafter abbreviated as DMF) and diphenylmethane-4,4'-cyisocyanate (hereinafter abbreviated as MDI) were weighed and heated from 1 to 70°C for 13 min while stirring.
Time reacted. First, A (in Table 1) is dicyclohexylmethane-4゜4'-diisocyanene-1-
(hereinafter abbreviated as CHMDI) 47.20B, B is CIM
7.9 parts of DI, 28.3 parts of CIIMDI for C, and hexane-1,6-dicyane 1- (hereinafter 11 DI) for D.
18.1 parts of each were added and reacted at 70°C for 10 hours, and then heated to 25°C for 6. A polyurethane elastomer solution with a viscosity of PO to 900 voids was obtained. A diluted solution of 100 parts of these solutions with 200 parts of DMF was applied onto a polyethylene terephthalate film, and 9 parts of water was diluted with 200 parts of DMF.
After being immersed in a coagulating solution at 20°C consisting of 5% DMF and 5% DMF for 30 minutes to solidify, it was peeled off from the polyethylene terephthalate film, washed in warm water at 50°C to remove DMF, and dried to form a porous film. l- was obtained. The light resistance and nitrogen oxide gas resistance of these porous sheets were good as shown in Table 2.

Regarding light resistance, the test method showed the degree of coloration [grade 1 (most severe coloring) to grade 5 (no coloration at all)] after exposure to a carbon arc fade meter for 20 hours. Regarding nitrogen oxide gas resistance, the degree of coloring when exposed to nitrogen oxide gas was shown according to JIS L-0855.

Table 1/Example 2 (11Et4' machine, 300 parts of polytetramethylene ether glycol with a molecular weight of 2000, 54 parts of butane-1,4-diol, DMF1
Weigh out 235 parts and 1150 parts of MD, and add 70 parts while stirring.
After reacting at 70°C for 3 hours, 125.2 parts of HD was added and the reaction was further carried out at 70°C for 10 hours to obtain a polyurethane elastomer solution having a viscosity of 820 voids at 25°C. This solution was coagulated in the same manner as in Example] to obtain a porous sheet. There was this porous sheet.

Comparative Example 1 Molecular weight 2 (H
1-300 parts of polytetramethylene adibe of IO, 27.9 parts of ethylene glycol, 1115 parts of DMF and MD1
150 parts were weighed out and reacted at 70°C for 3 hours with stirring to obtain a polyurethane elastomer solution having a viscosity of 700 voices at 25°C. To 100 parts of this solution, 0.5 part of Irganox 0110 (Chiha Geigy) and 0.5 part of Sanol LS-770 (Sankyo) were added, and the mixture was wet coagulated in the same manner as in Example 1 to obtain a porous sheet.

The light resistance and nitrogen oxide gas resistance of this porous sheet were extremely poor as shown in Table 2.

Comparative Example 2 A Yotsuro flask with a molecular weight of 200 was equipped with a stirrer and a thermometer.
300 parts of polytetramethylene adipate, 27.9 parts of ethylene glycol, 1120 parts of DMF and CHMDI
47.2 parts and 5 parts of MDIIQ were weighed out and reacted at 70°C for 10 hours with stirring to obtain a polyurethane elastomer solution having a viscosity of 650 voids at 25°C. This solution was wet-coagulated in the same manner as in Example 1, but since the coagulation was slow and a good porous sheet could not be obtained, the immersion time in the coagulation solution was greatly extended to obtain a porous sheet. As shown in Table 2, the light resistance and nitrogen oxide gas resistance of this porous sheet were only slightly better than Comparative Example 2 using MDI alone.

Comparative Example 3 Molecular weight 200 was placed in a Yotsuro flask equipped with a stirrer and a thermometer.
0 polytetramethylene adipate 300 parts, ethylene glycol 27.9 parts, DMF 1122 parts, MD I
After weighing 90 parts and reacting at 70°C for 3 hours with stirring, 62.9 parts of CHMD I was added and the mixture was further reacted at 70°C for 1 hour.
The reaction was carried out for 0 hours to obtain a polyurethane elastomer solution having a viscosity of 850 voids at 25°C. This solution was wet-coagulated in the same manner as in Example 1, but the coagulation was slow and a good porous sheet could not be obtained.
A porous sheet was obtained by extending the soaking time to a large extent. The light resistance and nitrogen oxide gas resistance of this porous sheet were extremely good as shown in Table 2. However, the Western-style film forming property was poor as described above, and it was not suitable for industrial production.

Claims (1)

[Claims] 70 to 95 mol% of diphenylmethane-4,4'-diisocyanate is reacted with the polyol, and then 5
A polyurethane sheet material with little discoloration, which is obtained by applying a solution of a polyurethane elastomer obtained by reacting with ~30 mol % of a non-aromatic diisocyanate onto a substrate and forming a film into a porous structure by a wet coagulation method.