JPH04108820A - Production of non-yellowing polyurethane urea foam - Google Patents

Abstract

PURPOSE:To obtain the title low toxic foam excellent in mechanical properties, suitable as a material for medical, hygienic, clothing, food packaging uses by reaction between a specific isocyanate-terminated prepolymer and water in the presence of a carboxylic acid metal salt. CONSTITUTION:Firstly, (A) a prepolymer is prepared by addition reaction between (1) a bi to trifunctional polyol 100-5000 in average molecular weight (e.g. glycerol) and (2) 1.4-2.6 equivalent times the hydroxyl group in the component 1 of an aliphatic polyisocyanate such as hexamethylene diisocyanate. Thence, a mixture of the component A and (B) 0.7-5 equivalent times the isocyanate in the component A of water is incorporated with (C) 0.1-5 pts.wt. per 100 pts.wt. of the component A of a carboxylic acid metal salt (e.g. potassium octanoate) followed by reaction, thus obtaining the objective foam.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a non-yellowing polyurethaneurea foam useful as a material for medical, sanitary, clothing, food packaging, etc.

In recent years, polyurethane has been widely used in various fields as elastic bodies, foams, adhesives, etc. In particular, when used in fields such as medical, sanitary, clothing, and food packaging, polyurethane is required to have low toxicity and, in some cases, non-yellowing.

Polyurethane is usually produced by reacting polyisocyanates and polyols in the presence of curing catalysts such as amines, organometallic compounds, metal salts, etc. Catalysts are highly toxic and may migrate to the polyurethane surface, so they are not preferred for applications that require low toxicity, such as medical, sanitary, clothing, and food packaging applications. On the other hand, fatty acid metal salts, especially potassium salts and sodium salts, have low toxicity and are known as trimerization catalysts for isocyanate groups, but they are generally more active than amines and organometallic compounds as urethanation catalysts. is low and requires combination with other catalysts to obtain rapid curing rates. Furthermore, the resulting polyurethane has drawbacks such as brittleness and lack of flexibility.

Regarding isocyanates, diphenylmethane diisocyanate (MDI), which is often used as a raw material for polyurethane, and tolylene diisocyanate (T
Aromatic isocyanates such as DI) are generally difficult to metabolize in the body, and aromatic amines, which are metabolites, are suspected of being carcinogenic, so they are preferable for applications that require low toxicity. No [e.g. Chris Ba
tich, Jerry Williams and
Roy King, Applied Biomate
reals, Vol., 23. No, A3.31
2-319 (1989).

On the other hand, conventional methods for producing non-yellowing polyurethane foam include the so-called one-shot method, in which aliphatic polyisocyanate, polyol, curing catalyst, and water are mixed, stirred, and cured. [For example, Japanese Patent Publication No. 52-30437, Japanese Unexamined Patent Publication No. 128994-1982, Japanese Patent Publication No. 54-1]
See Publication No. 5599 1゜However, since aliphatic isocyanates generally have lower reactivity than aromatic isocyanates, amines and organometallic compounds are used as curing catalysts, which have high activity but are problematic in terms of toxicity. Must. Furthermore, when using the one-shot method, the reaction heat during the curing reaction is larger than that of the so-called "prepolymer method" in which a prepolymer obtained by adding polyisocyanate to a polyol in advance is cured. Therefore, when producing a large foam, the one-shot method raises the temperature inside the foam too much, making it difficult to control the reaction and making it difficult to obtain a uniform foam.

As mentioned above, aliphatic isocyanates generally have lower reactivity than aromatic isocyanates, and when they are made into a prepolymer, the mobility of the molecules further decreases, resulting in a further decrease in reactivity. Therefore, conventionally, a method of producing polyurethane foam by a prepolymer method using an aliphatic isocyanate has not generally been used.

In order to enable polyurethane foam to be used in applications requiring low toxicity, the present inventors have conducted intensive studies on a method for producing polyurethane foam using a prepolymer method using aliphatic isocyanates. A prepolymer having isocyanate groups at substantially all molecular ends obtained by addition-reacting a polyol with a specific molecular weight and number of functional groups with an aliphatic polyisocyanate in a specific ratio is used, and this is mixed with water in a specific ratio. We have discovered that when reacting, it can be cured quickly even in the presence of a low-toxic carboxylic acid metal salt without using a highly toxic curing catalyst, and a foam with excellent mechanical properties can be obtained. The present invention has now been completed.

Thus, according to the invention, the average molecular weight is between 100 and 5,
000 and a 2- to 3-functional (average value) polyol with an isocyanate-terminated prepolymer obtained by addition-reacting an aliphatic polyisocyanate in an amount of 1.4 to 2.6 times the hydroxyl equivalent of the polyol; 0 of isocyanate equivalent
．． A method for producing a non-yellowing polyurethaneurea foam, which comprises reacting 7 to 5 times the amount of water in the presence of 0.1 to 5 parts by weight of a carboxylic acid metal salt per 100 parts by weight of the prepolymer. is provided.

The method of the present invention will be explained in more detail below.

The aliphatic polyisocyanate used in the preparation of the isocyanate-terminated prepolymer used in the present invention is not limited to only those consisting of aliphatic chains, but may also be alicyclic polyisocyanates. An aromatic ring may be present in the aliphatic chain, and specific examples include hexamethylene diisocyanate, hexamethylene triisocyanate, bicycloheptane triisocyanate,
Undecane triisocyanate, lysine ester triisocyanate, inphorone diisocyanate, dicyclohexylmethane diisocyanate, methylcyclohexane diisocyanate, dimethylcyclohexane diisocyanate, xylylene diisocyanate, tetramethylxylene diisocyanate, or two of these. Examples include mer, dimer, and the like. Among these, hexamethylene diisocyanate is particularly preferred.

On the other hand, the polyol used in the prepolymerization of the aliphatic polyisocyanate has an average molecular weight of 100 to 5,000, preferably 200 to 3,000.
A polyol is used which is within the range of 2 to 3 and has an average number of functional groups of 2 to 3.

When the average molecular weight of the polyol used is 100 ends,
When a polyisocyanate is added to form a prepolymer, the proportion of hydrophobic parts in the prepolymer increases, and the miscibility of water to be reacted with becomes poor, making it difficult for the curing reaction to proceed. On the other hand, if it exceeds 5,000, the density of the terminal isocyanate groups of the prepolymer becomes small, the reaction frequency decreases, and the progress of the curing reaction tends to be slow.

Such polyols include, for example, divalent or trivalent alcohols (e.g., ethylene glycol, propylene glycol, glycerin, hexanetriol, triethanolamine, etc.) and alkylene oxides (e.g.,
Polyethylene oxide, polypropylene oxide, poly(ethylene oxide-propylene oxide) copolymer obtained by adding ethylene oxide, propylene oxide, butylene oxide, etc.), polytetramethylene ether glycol obtained by ring-opening polymerization of tetrahydrofuran, etc. Polyether polyols; dihydric or trihydric alcohols as above, caprolactone,
Lactone-based polyester polyols obtained by ring-opening addition of lactones such as glycolide and lactide, condensation of hydroxycarboxylic acids (e.g., glycolic acid, lactic acid, salicylic acid, etc.) with dihydric or trihydric alcohols such as those mentioned above. Compounds obtained by condensing dicarboxylic acids (e.g., oxalic acid, allonic acid, succinic acid, glutaric acid, phthalic acid, adipic acid, etc.) with diols (e.g., ethylene glycol, propylene glycol, etc.) Compound,
Included are polyester polyols such as condensed polyester polyols obtained by adding diols to acid anhydrides (for example, phthalic anhydride).

The above-mentioned prepolymer from the aliphatic polyisocyanate and polyol can be prepared by subjecting the two to an addition reaction by a method known per se. At this time, the reaction ratio between polyisocyanate and polyol is NGO/.

It is important that the H ratio is within the range of 1.4 to 2.6, preferably 1.5 to 2.5. If the ratio is smaller than 1.4, the resulting prepolymer tends to have a high molecular weight and its viscosity increases, making stirring and mixing during curing difficult.
If it exceeds 2.6, the reaction between the hydrophobic aliphatic polyisocyanate monomer remaining in the obtained prepolymer and water and the reaction between the prepolymer and water will be uneven due to the difference in affinity with water. As the process progresses, there is a greater tendency for the cured product to become non-uniform.

Note that if the NCO/○H ratio is 2 or more, unreacted aliphatic polyisocyanate will remain in the prepolymer, but in this case, the remaining polyisocyanate monomer may be added to the prepolymer as necessary. A portion or substantially all of it may be removed from the polymer, or it may remain in the prepolymer without any problem.

In this way, a prepolymer having isocyanate groups at substantially all of the molecular ends is obtained.

According to the invention, the prepolymer is reacted with water in the presence of a curing catalyst. This curing reaction proceeds by chain extension accompanied by a urea bond produced by the reaction of the amino group produced by the reaction of the terminal isocyanate group of the prepolymer with water and the terminal isocyanate group of another prepolymer.

The amount of water used in the reaction is 0.7 to 5 times the isocyanate equivalent in the prepolymer, preferably 0.8 to 4.
It can be within the range of 5 times the amount.

If the amount of water is less than 0.7 times the amount, many unreacted isocyanate groups will remain and a good foam will not be obtained, while if it exceeds 5 times the amount, the foam will be formed due to the reaction between the isocyanate groups and water. A problem arises in that the isocyanate-terminated prepolymer molecules to be reacted are not present in the vicinity of the amino-terminated prepolymer molecules, and the chain extension reaction is not carried out sufficiently, resulting in only a non-uniform cured product.

In the method of the present invention in which curing is carried out using urea bonds produced by the reaction of aliphatic polyisocyanate and water, it is of course possible to use highly active curing catalysts such as amines and organometallic compounds. It has been found that the curing reaction proceeds rapidly even when a low toxicity carboxylic acid metal salt is used.

Usable metal carboxylic acid salts include alkali metal salts, lead salts, calcium salts, etc. of aliphatic carboxylic acids, and potassium salts or sodium salts are particularly suitable.

Such carboxylic acid metal salts can generally be used in an amount of 0.1 to 5 parts by weight, preferably 1 to 3 parts by weight, per 100 parts by weight of the prepolymer. If the amount of carboxylic acid metal salt used is less than 0.1 part by weight, the curing reaction will not proceed quickly, and if it is more than 5 parts, the reaction will proceed too quickly, making it difficult to obtain a uniform cured product. .

In addition, when producing foams for applications where toxicity is not a major problem, carboxylic acid metal salts can be used with ordinary urethanization catalysts, such as monoamines such as triethylamine, dimethylcyclohexylamine, tetramethylethylenediamine, tetramethylhexanediamine, etc. Diamines: triamines such as tetramethylguanidine; cyclic amines such as triethylenediamine, dimethylpiperazine, methylmorpholine; alcohol amines such as dimethylaminoethanol, trimethylaminoethylethanolamine, hydroxyethylmorpholine; ether amines such as bisdimethylaminoethyl ether It can also be used in combination with organic tin compounds such as stannath octoate, dibutylquine diacetate, and dibutylquine dilaurate; and organic lead compounds such as lead octenoate.

In the method of the present invention, two or more prepolymers having different isocyanate components and/or polyol components may be mixed and used, and if necessary, the curing reaction system may be added with the above-mentioned prepolymers. Average molecular weight is 100-5,00
Polyols having an average number of functional groups of 2 to 3 may be added. Thereby, the prepolymer, water,
It becomes possible to adjust the viscosity of a foaming solution containing a catalyst, promote compatibilization, etc., and also adjust the physical properties of the resulting cured product. Therefore, the amount of the polyol added is usually such that the hydroxyl equivalent of the polyol is 30% or less, preferably 15% or less of the isocyanate equivalent of the prepolymer.

Furthermore, in the method of the present invention, auxiliary agents such as foam stabilizers, blowing agents, flame retardants, chain extenders, crosslinking agents, and fillers are added as appropriate, as is often done in the production of ordinary polyurethane. May be blended.

The polyurethane urea foam produced by the method of the present invention does not need to contain aromatic rings as long as the hard segment part made of urea bonds and urethane bonds is balanced with the soft segment part made of polyol, methylene groups, etc. It shows good mechanical properties, but if necessary, it can be improved by using aliphatic polyisocyanates or polyols containing compounds that have aromatic rings, urethane bonds, urea bonds, ester bonds, etc. that can become hard segment parts in the molecule. It exhibits mechanical properties. It is also possible to form foams.

The polyurethaneurea foam produced by the method of the present invention is characterized by the fact that it can be foamed with a less toxic catalyst and does not yellow compared to conventional polyurethane foams using aromatic isocyanates. There is. In addition, compared to polyurethane foam using aliphatic isocyanate,
It has advantages such as milder foaming conditions and the ability to easily obtain large foams. Since the foam provided by the present invention has low toxicity, it can be used in applications that come into direct contact with the human body or food, such as medical materials such as casts and elastic bandages, and cushioning materials for food packaging. It can also be used in applications where non-yellowing is desired, such as clothing materials such as shoulder pads and bra pads.

Next, the present invention will be explained in more detail with reference to Examples.

Examples 1 to 3 and Comparative Examples 1.2 (8) Prepolymer Preparation HDI [hexamethylene diisocyanate: Nippon Polyurethane Co., Ltd. 13
36. Charge L9, heat to 80°C, and stir. Add Carpowax #400 [polyethylene glycol;
Kokusan Kagaku Co., Ltd. 140i having an average molecular weight of 400 is added dropwise over 3 hours (NCo10H equivalent ratio -2). After the dropwise addition, the mixture was further stirred at 80°C for 6 hours to obtain Prepolymer A.

In addition, instead of Carpowax #400 in the above method, Sannix G having the same hydroxyl equivalent as the polyol was used.
L-3000 [trifunctional polyether polyol; average molecular weight 3000, Sanyo Chemical Industries, Ltd.], Sasanlux PP-400 [bifunctional polyether polyol: average molecular weight 400, Sanyo Chemical Industries, Ltd.], Plaxel 20
5AL [bifunctional polyester polyol; average molecular weight 500, Daicel Chemical Industries, Ltd.] or Fandol P
Prepolymers BSC, D and E were prepared respectively in the same manner as above except that L~305 [bifunctional polyester polyol; average molecular weight 350, Toho Rika Kogyo Co., Ltd.] was used.

Furthermore, in place of MDI in the above method, the same number of moles of desmodur W [dicyclohexylmethane-4,4'
- Sea Isocyaner); Resident Bayer Urethane Co., Ltd.
] except for using prepolymer F
was prepared.

Furthermore, in the same manner as above, Sanix PP400 and M
Prepolymers G and H were obtained by reacting with DI at an NCO/○H equivalent ratio of 1.5 or 2.5, respectively.

(B) Preparation of catalyst and foam stabilizer 1 part by weight of potassium octoate salt was dissolved in part by weight of TG-400 [polyether polyol; Mitsui Nisso Co., Ltd.] to obtain catalyst M, and 1 part by weight of sodium acetate salt. 1 part by weight of water
A silicone oil L-5430 [Nippon Unicar Co., Ltd. or 5H-193 [Dow Conning Silicon Co., Ltd.] was prepared as a foam stabilizer.

(C) Preparation of polyurethaneurea foam Water, a catalyst, and a foam stabilizer were added to the obtained aliphatic isocyanate-terminated prepolymer to perform foaming. All foaming is done at room temperature (25 degrees Celsius)
).

In Examples 1 to 3, 102 cups of prepolymer A were added, and the amounts of catalyst, foam stabilizer, and water listed in Table 1 were added, and the mixture was stirred for 10 seconds at a rotational speed of 200 rpm using a cage mixer. The amount of water added was equal to the isocyanate equivalent in Example 1, 4.5 times the isocyanate equivalent in Example 2, and 0.8 times the isocyanate equivalent in Example 3.

The resulting mixture was sandwiched between two glass plates held at a distance of 1 mm by a spacer, and cured between them to obtain a foamed sheet-like sample. During this time, the curing time was measured. The term "curing time" as used herein means the time required for the foam to form (quiz) and become tack-free through a curing reaction. In addition, a tensile test of the cured product was conducted. The pulling speed was 10 cm for 7 minutes.

As Comparative Example 1, curing was attempted using the same raw materials as in Example 1 using the one-shot method without using the prepolymer method without changing other conditions. That is, instead of prepolymer A107, Carpowax #400 was used at 5°4.9, and MDI was 4.5.
? , water and 0.241 catalyst MO912 were mixed and stirred to perform curing. Furthermore, as Comparative Example 2, instead of chain extension using urea bonds, chain extension using urethane bonds was attempted. That is, 0.92% of ethylene glycol was added to prepolymer A.
, 0.12% of Catalyst M was added, and curing by urethane bonding was performed without changing other conditions.

The results are summarized in Table 1 below.

table".

Examples 4 to 12 Prepolymer 400'j was placed in a cup, water, catalyst, and polyol (Sannix GL-30) were added in the amounts listed in Table 2.
00) and a foam stabilizer were added, and the mixture was stirred for 20 seconds at a rotational speed of 2000 rpm using a cage mixer. This is 25 per side
The mixture was injected into a three-dimensional box with a diameter of 1 cm and was foamed and cured.

The curing time, core density and foam condition of the obtained foam are summarized in Table 2 below.

Procedural proceedings (spontaneous) September 5, 1991 Wataru Fukasawa, Commissioner of the Japan Patent Office1, Indication of the case, 1990 Patent Application No. 2223862, Title of the invention: Process for producing non-yellowing polyurethane urea foam 3. Relationship with the case of the person making the amendment Patent applicant name (437) Nisshinbo Co., Ltd. 4. Agent 〒107 5. No date of amendment order 6. Subject of amendment 120 = 7 Contents of amendment (1) The present application Claims (Description, page 1, 5-18
line) as shown in the attached sheet.

(2) On page 6, line 8 of the specification, the phrase "used for preparation" is corrected to "used for preparation."

(3) On page 14, line 4 of the same page, the phrase ``indicated foam'' is corrected to ``indicated foam.''

(4) On page 15, line 13 of the same page, delete the phrase ``same hydroxyl group equivalent''.

(5) In the second line from the bottom of page 16, the words "obtained." are corrected to "obtained."

(6) On page 18, lines 8 and 12, “OIgJ is corrected to ro, 5gJ.

(7) In the fourth line from the bottom of page 19, the word "solid body" is corrected to "cube."

(8) Table 2 on page 20 of the same page is corrected as follows.

(Attachment) [Claims] "1. A bifunctional polyol with an average molecular weight of 100 to 5,000 and an aliphatic polyisocyanate in an amount of 1.4 to 2.6 times the hydroxyl equivalent of the polyol. An isocyanate-terminated prepolymer obtained by addition reaction and water in an amount of 0.7 to 5 times the isocyanate equivalent in the presence of 0.1 to 5 parts by weight of a carboxylic acid metal salt per 100 parts by weight of the prepolymer. 1. A method for producing a non-yellowing polyurethaneurea foam, which comprises reacting the following:

2. The method according to claim 1, wherein the aliphatic polyisocyanate is 1,6-hexamethylene diisocyanate.

3. The method according to claim 1, wherein the carboxylic acid salt is a potassium salt or a sodium salt of an aliphatic carboxylic acid. ”

Claims (1)

[Claims] 1. Addition reaction of a di- to trifunctional polyol with an average molecular weight of 100 to 5,000 and an aliphatic polyisocyanate in an amount of 1.4 to 2.6 times its hydroxyl equivalent. The isocyanate-terminated prepolymer obtained by the method and water in an amount of 0.7 to 5 times the isocyanate equivalent are added in the presence of 0.1 to 5 parts by weight of a carboxylic acid metal salt per 100 parts by weight of the prepolymer. A method for producing a non-yellowing polyurethaneurea foam, which comprises reacting. 2. The method according to claim 1, wherein the aliphatic polyisocyanate is 1,6-hexamethylene diisocyanate. 3. The method according to claim 1, wherein the carboxylic acid salt is a potassium salt or a sodium salt of an aliphatic carboxylic acid.