JPH04239016A - Production of nonyellowing polyurethane urea foam - Google Patents

Abstract

PURPOSE:To obtain the title foam useful as a clothing material or a food packaging material by reacting a specified isocyanate-terminated prepolymer with water in the presence of an amine catalyst. CONSTITUTION:A polyol (e.g. polypropylene glycol) of a number-average molecular weight of 100-5000 and an average functionality of 2-3 is reacted with an aliphatic polyisocyanate (e.g. 1,6-hexamethylene diisocyanate) in an amount 1.4-2.5 times as large as that of the hydroxyl equivalent of the polyol to obtain an isocyanate-terminated prepolymer (A). The title foam is obtained by reacting component A with water in an amount 0.4-5 times as large as that of the NCO equivalent of component A in the presence of an amine catalyst, desirably a diazabicycloalkene of the formula (wherein m is 3-7; and n is 2-4) or a salt thereof with an organic acid in an amount of 0.1-10 pts.wt. per 100 pts.wt. component A.

Description

[Detailed description of the invention]

The present invention relates to a method for producing a non-yellowing polyurethaneurea foam useful in the fields of clothing materials, food packaging materials, and the like.

[0002] Polyurethane is widely used in various fields as foams, elastic bodies, adhesives, etc., and there are applications that require non-yellowing properties, especially in the fields of clothing materials, food packaging materials, etc. .

[0003] Polyurethanes are usually produced by reacting polyisocyanates and polyols in the presence of curing catalysts such as amines, organometallic compounds, metal salts, and the like. When producing foams, a rapid reaction rate is required, but polyurethanes using aromatic polyisocyanates with high reaction activity have the disadvantage of yellowing when exposed to light, oxygen, etc. On the other hand, although polyurethanes using aliphatic polyisocyanates have yellowing resistance, it is difficult to use them for producing foams due to the low reaction activity of aliphatic polyisocyanates.

Conventionally, as a method for producing non-yellowing polyurethane foam, an aliphatic polyisocyanate and a polyol are mixed with two selected from amines, metal salts and organometallic compounds.
A method has been proposed for producing polyurethane foam using the so-called "one-shot method," in which the foam is mixed with a curing catalyst consisting of a specific combination of more than one type of compounds and water as a swelling agent (foaming agent), stirred, and cured ( For example, Tokuko Sho 5
Publication No. 2-30437, JP-A-52-128994,
Japanese Patent Publication No. 54-15599, Japanese Patent Publication No. 2-25581
(See Publication No. 7, etc.)

[0005] The one-shot method is more difficult than the so-called prepolymer method, in which a prepolymer obtained by adding polyisocyanate to a polyol in advance is cured.
The heat of reaction during curing is large, allowing the curing reaction to proceed more quickly. Therefore, when producing large foams or adding a large amount of water to the reaction system, it is difficult to control the reaction even when using aliphatic isocyanates with low reactivity, and due to the reaction heat. There is a problem in that the temperature inside the foam increases too much, causing, for example, discoloration inside the foam, making it difficult to obtain a good foam.

On the other hand, as mentioned above, aliphatic isocyanates generally have lower reactivity than aromatic isocyanates;
Prepolymerization further reduces the mobility of molecules, which further reduces reactivity. Therefore, conventionally, a method of producing a foam by a prepolymer method using an aliphatic polyisocyanate has not generally been used.

[0007] The present inventors have conducted extensive studies on a method for producing foams using a prepolymer method using aliphatic polyisocyanates. By using a prepolymer that has isocyanate groups at substantially all molecular ends obtained by addition reaction at a certain ratio, and reacting it with a specific amount of water, the reaction can be rapidly performed even in the presence of an amine-based catalyst only. It was discovered that a good foam with excellent mechanical properties could be obtained by curing, and the present invention was completed.

Thus, according to the present invention, a polyol having a number average molecular weight of 100 to 5,000 and an average number of functional groups of 2 to 3 is added with an aliphatic polyisocyanate in an amount of 1.4 to 2.6 times its hydroxyl equivalent. The isocyanate-terminated prepolymer obtained by reacting the isocyanate-terminated prepolymer in the presence of water in an amount of 0.4 to 5 times the isocyanate equivalent and 0.1 to 10 parts by weight of an amine catalyst per 100 parts by weight of the prepolymer. Provided is a method for producing a non-yellowing polyurethaneurea foam, which is characterized by reacting with.

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

The polyol used to prepare the isocyanate-terminated prepolymer as a raw material has a number average molecular weight of 100.
-5000, preferably 200-3000, and the average number of functional groups is 2-3. When the number average molecular weight of the polyol used is less than 100, when polyisocyanate is added to form a prepolymer,
The proportion of hydrophobic parts in the prepolymer increases, and the miscibility with the water to be reacted deteriorates, 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. Therefore, as polyols that can be used in the present invention, for example, (a
) dihydric or trihydric alcohols (e.g. ethylene glycol, propylene glycol, glycerin, hexanetriol, triethanolamine, etc.) and alkylene oxides (e.g. ethylene oxide, propylene oxide,
butylene oxide, etc.) [e.g. polyethylene oxide, polypropylene oxide, poly(ethylene oxide-propylene oxide) copolymer]; polyether polyols such as polytetramethylene ether glycol obtained by ring-opening polymerization of tetrahydrofuran; b) Lactone-based polyester polyol obtained by ring-opening addition of caprolactone to a dihydric or trihydric alcohol as described above; condensing a hydroxycarboxylic acid (such as salicylic acid) to a dihydric or trihydric alcohol as described above Compounds obtained by combining dicarboxylic acids (for example, oxalic acid, malonic acid, succinic acid, glutaric acid, phthalic acid, adipic acid, etc.) with diols (
Compounds obtained by condensing ethylene glycol, propylene glycol, etc.); acid anhydrides (
For example, polyester polyols such as condensed polyester polyols obtained by adding the above diols to (eg, phthalic anhydride) can be mentioned.

On the other hand, the aliphatic polyisocyanate that can be reacted with the above-mentioned polyol is not limited to those consisting only of aliphatic chains, but may also be alicyclic ones, and furthermore, the aliphatic polyisocyanates containing aromatic A ring may be present. Specifically, hexamethylene diisocyanate, hexamethylene triisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, cyclohexylmethane diisocyanate, cyclohexyl diisocyanate, xylylene diisocyanate, etc.
Alternatively, dimers and trimers of these isocyanates can be mentioned. Among these, hexamethylene diisocyanate is particularly preferred.

The above-mentioned prepolymer from the aliphatic polyisocyanate and polyol can be prepared by addition reaction of the two by a method known per se. In this case, it is important that the reaction ratio between the polyisocyanate and the polyol is such that the NCO/OH ratio is within the range of 1.4 to 2.6, preferably 1.5 to 2.5. When 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. On the other hand, when the ratio exceeds 2.6, the reaction between the hydrophobic aliphatic polyisocyanate monomer and water present in the obtained prepolymer and the reaction between the prepolymer and water is reduced due to the difference in affinity with water. The process progresses unevenly, and the cured product tends to be uneven.

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 can range from 0.4 to 5 times, preferably from 0.5 to 4.5 times, the amount of isocyanate equivalent in the prepolymer. If the amount of water is less than 0.4 times the amount, many unreacted isocyanate groups remain and a good foam cannot be obtained, whereas if the amount exceeds 5 times the amount, amino-terminated prepolymer is produced by the reaction between isocyanate groups and water. A problem arises in that the isocyanate-terminated prepolymer molecule to be reacted is not present in the vicinity of the molecule, and the chain extension reaction is not sufficiently carried out, resulting in a non-uniform cured product.

In the method of the present invention in which curing is effected by urea bonds produced by the reaction of aliphatic polyisocyanate and water, amine catalysts commonly used in the urethane field, particularly tertiary amines, are used as catalysts. can do. Such tertiary amines include monoamines (e.g. triethylamine, dimethylcyclohexylamine, etc.), diamines (e.g. tetramethylethylenediamine, tetramethylhexanediamine, etc.), triamines (e.g. tetramethylguanidine, etc.), and cyclic amines (e.g. tetramethylguanidine, etc.). (e.g. triethylenediamine, dimethylpiperazine, methylmorpholine, etc.), alcohol amines (e.g. dimethylaminoethanol, trimethylaminoethylethanolamine, hydroxyethylmorpholine, etc.)
, ether amines (e.g. bisdimethylaminoethyl ether), diazabicycloalkenes [e.g.
,5-diazabicyclo(5,4,0)undecene-7(
DBU), 1,5-diazabicyclo(4,3,0)nonene-5, etc.], organic acid salts of diazabicycloalkenes (
Examples include DBU phenol salt, 2-ethylhexanoate, formate, etc.). Especially the following formula (I)

[0016]

[Case 2]

In the formula, m is an integer from 3 to 7, and n is from 2 to
Diazabicycloalkenes represented by and their salts with organic acids are preferred. Each of these amines can be used alone, or two or more kinds can be used in combination depending on the case.

The amine catalyst is generally used in an amount of 0.1 to 10 parts by weight, preferably 0.1 to 10 parts by weight per 100 parts by weight of prepolymer.
．． It can be used within the range of 4 to 4 parts by weight. If the amount of the amine catalyst used is less than 0.1 part by weight, the curing reaction will not proceed quickly, and if it is more than 10 parts by weight, it will be uneconomical, and furthermore, the curing reaction will proceed too quickly and a uniform cured product will not be obtained. The problem is that it is difficult to obtain.

In the method of the present invention, two or more prepolymers having different isocyanate components and/or polyol components may be used as a mixture, and if necessary, the curing reaction system may include the above-mentioned prepolymers. Number average molecular weight is 10
Within the range of 0 to 5000 and the average number of functional groups is 2 to 3
Polyols may also be added. This makes it possible to adjust the viscosity and promote compatibilization of the foaming stock solution consisting of prepolymer, water, catalyst, etc., and also to adjust the physical properties of the resulting cured product. Even in the case of the present invention, in which chain extension is carried out primarily through the formation of urea bonds through the reaction between isocyanate groups and water, it is possible to incorporate polyols into the cured product through the formation of urethane bonds through the reaction between hydroxyl groups and isocyanate groups. . Therefore, the amount of the polyol added is usually such that the hydroxyl equivalent of the polyol is 60% or less of the isocyanate equivalent of the prepolymer, preferably 5% or less of the isocyanate equivalent of the prepolymer.
It can be set to 0% or less. When the amount is more than 60%, a problem arises in that the reaction rate decreases and it is difficult to obtain a cured foam product.

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 used, as is often done in the production of ordinary polyurethane. Agents may be added as appropriate.

[0021] Further, the foam may be heated and post-cured for the purpose of reacting the isocyanate groups remaining after foaming.

The polyurethane urea foam produced by the method of the present invention exhibits good mechanical properties as long as the hard segment portion consisting of urea bonds and urethane bonds and the soft segment portion consisting of polyol, methylene groups, etc. are well balanced. show.

The polyurethaneurea foam produced by the method of the present invention is characterized in that it does not yellow compared to conventional foams using aromatic isocyanates. Furthermore, compared to polyurethane foams using aliphatic isocyanates, they have the advantage that foaming conditions are milder and larger foams can be easily obtained. Thus, the foams provided by the present invention can be used in applications where non-yellowing is desired, such as padding, clothing materials such as bra padding, or also food packaging materials.

[0024] Next, the present invention will be explained in more detail with reference to Examples.

[0025]

[Example] Examples 1 to 12 and Comparative Examples 1 and 2 (A) Preparation of prepolymer HDI [1,6-hexamethylene diisocyanate; Nippon Polyurethane Co., Ltd.] was placed in a four-necked flask equipped with a cooling tube.
] 336.4 g and 400 g of Sannix PP400 [polypropylene glycol; number average molecular weight 400, Sanyo Chemical Industries, Ltd.] (NCO/OH equivalent ratio = 2).
, and raise the temperature to 100°C while stirring. After a while, the temperature inside the system rises due to the exothermic reaction, but as the reaction ends, the temperature inside the system drops. When the temperature dropped to 120°C, stirring was continued for 4 hours at a constant temperature of 120°C to obtain Prepolymer A. The NCO% of this product was theoretically 11.4%, whereas the value measured by the dibutylamine method was 10.9%.

[0026] Furthermore, Sunnix PP in the above method
Sunnix GL as polyol instead of 400
-3000 [functional polyol; number average molecular weight 3000
, Sanyo Chemical Industries, Ltd.] Plaxel 205AL [bifunctional polyester polyol; number average molecular weight 500, Daicel Chemical Industries, Ltd.] or Sannix PP-1000
Prepolymers B, C, and D were prepared in the same manner as above except for using (bifunctional polyol; number average molecular weight 1000, Sanyo Chemical Industries, Ltd.).

Furthermore, in the same manner as above, Sunnix P
Prepolymers E and F were prepared by reacting P400 and HDI at NCO/OH equivalent ratios of 1.5 or 2.5, respectively.

(B) Catalyst and foam stabilizer DBU[1,5-diazabicyclo(5,4
, 0) Undecene-7, manufactured by Sun-Apro Co., Ltd.], SA-
102 [DBU 2-ethylhexanoate, San-Apro (
Co., Ltd.], SA-1 [phenol salt of DBU, San-Apro Co., Ltd.], DBN [1,5-diazabicyclo(4,
3,0) Nonene-5, manufactured by San-Apro Co., Ltd.] was prepared.

As a foam stabilizer, SH-193 [manufactured by Dow Corning Toray Silicone Co., Ltd.] was prepared.

(C) Preparation of polyurethaneurea foam Water, a catalyst, and a foam stabilizer were added to the aliphatic isocyanate-terminated prepolymer obtained in (A) above, and foaming was performed. Stirring was carried out using a cage mixer at a rotation speed of 2000 rpm for 10 seconds. All foaming was done at room temperature (25 degrees Celsius).

In Examples 1 to 4, water, catalyst, polyol and foam stabilizer in the amounts listed in Table 1 were added to 100 g of Prepolymer A in a cup. The amount of water added was equal to the isocyanate equivalent in Example 1, 4.4 times the isocyanate equivalent in Example 2, and 0.5 times the isocyanate equivalent in Example 3. In Example 4, curing was performed using the composition shown in Table 1. The amount of PEG400 added was 0.5 times the isocyanate equivalent. The curing speed and core density of the obtained foam are summarized in Table 1.

In Examples 5 to 7, a different catalyst from Example 1 was used for curing. Water and foam stabilizer were dissolved in SANNIX GL-3000 in advance [Water/GL-3000=
1/5 (weight ratio), SH-193/GL-3000=1
/4 (weight ratio)] was added. The composition, curing time, curing speed and core density of the obtained foam are summarized in Table 2.

In Examples 8 to 10, curing was performed using a prepolymer synthesized from a polyol different from that in Example 1. Water and foam stabilizer were dissolved in SANNIX GL-3000 in advance [Water/GL-3000=1/5 (weight ratio)
, SH-193/GL-3000=1/4 (weight ratio)]
was added. The composition, curing time, core density and foam state of the obtained foam are summarized in Table 2.

In Examples 11 and 12, curing was performed using prepolymers obtained by changing the charging ratio of HDI and Sannix PP400 during prepolymer synthesis compared to Example 1. Water and foam stabilizer were dissolved in SANNIX GL-3000 in advance [Water/GL-3000=1/5 (weight ratio)
, SH-193/GL-3000=1/4 (weight ratio)]
was added. The composition, curing time, curing speed and core density of the obtained foam are summarized in Table 2.

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, prepolymer A100
Curing was attempted using Sunnix PP-400 and HDI in place of g and the compositions listed in Table 1. Also, comparative example 2
Therefore, instead of chain extension using urea bonds, we attempted chain extension using urethane bonds. That is, ethylene glycol in an amount equivalent to isocyanate was added to Prepolymer A instead of water, and curing by urethane bonding was attempted using the compositions in the amounts listed in Table 1. The results are summarized in Table 1.

[0036]

[Table 1] *Not observed because it did not harden.

[0037]

[Table 2]

Claims (3)

[Claims] Claim 1: By subjecting a polyol having a number average molecular weight of 100 to 5,000 and an average number of functional groups of 2 to 3 to an addition reaction with an aliphatic polyisocyanate in an amount of 1.4 to 2.6 times the hydroxyl equivalent of the polyol. The obtained isocyanate-terminated prepolymer is mixed with water in an amount of 0.4 to 5 times the isocyanate equivalent and 0.1 to 1 part by weight per 100 parts by weight of the prepolymer.
A method for producing a non-yellowing polyurethaneurea foam, which comprises reacting in the presence of 0 parts by weight of an amine catalyst. [Claim 2] The aliphatic polyisocyanate is 1,6
-hexamethylene diisocyanate. 3. The amine catalyst is a diazabicycloalkene or an organic compound thereof represented by the formula (I), wherein m is an integer of 3 to 7, and n is an integer of 2 to 4. The method according to claim 1 or 2, which is a salt with an acid.