JPS6353209B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to aliphatic liquid urethane prepolymers with isocyanate terminals at both ends. More specifically, hexamethylene diisocyanate has a content of 0.7% by weight, obtained by reacting hexamethylene diisocyanate with a branched alkylene diol having 3 to 10 carbon atoms at an NCO/OH molar ratio of 8 or more, and purifying to remove excess diisocyanate. % or less, and
This invention relates to a liquid urethane prepolymer with isocyanate terminals at both ends and aliphatic liquid urethane prepolymer having a viscosity at 25°C of 5000 cps or less. Conventionally, polyurethanes that utilize the reaction between isocyanate groups and active hydrogen compounds, particularly alcohols or amines, have been applied to paints, foaming materials, adhesives, sealants, etc., and have exhibited excellent performance. In the field of paints, it is common to avoid aromatic isocyanates, which are prone to yellowing, as isocyanate components because they are exposed to sunlight, wind and rain, and to use aliphatic isocyanates to increase the weather resistance of paints. Since the aliphatic diisocyanates used as raw materials for these paints are highly toxic and irritating, they are used in the form of polymerized polyisocyanates that are free of toxicity and irritating properties. Commonly used aliphatic polyisocyanates for coatings include hexamethylene diisocyanate (HMDI), pure polyisocyanate,
There are HMDI-trimethylolpropane adduct polyisocyanates, but all of these are polymeric compositions containing three or more isocyanate groups in one molecule. On the other hand, in the field of foamed materials and adhesives, aromatic bifunctional materials such as diphenylmethane diisocyanate (MDI), modified MDI, and tolylene diisocyanate have traditionally been used, as weather resistance, especially yellowing, has not been much of a problem. isocyanates have been used. These foam materials and adhesives, especially those described below,
In the field of automotive interior parts and food packaging adhesives using the RIM process, polyurethane resins are required to have appropriate elasticity and flexibility, so difunctional aromatic isocyanates are often used. However, in recent years in the field of foam materials, due to the development of the RIM process, yellowing of foams using aromatic isocyanates has become a major problem, for example in automobile interior parts, and there is a strong demand for no yellowing. Strong against Furthermore, in the adhesive field, there is a strong demand for non-yellowing for shoe soles, adhesives, food packaging adhesives, etc., and in the food packaging field, aromatic amines, which are hydrolysis products of aromatic polyurethane, are carcinogenic. has become a problem, and there is a strong demand to replace the isocyanate component with an aliphatic one. When replacing the aromatic isocyanates used in the fields of foam materials, adhesives, etc. with aliphatic isocyanates, they are used in the paint field mentioned above.
When using HMDI-type polyisocyanate with three or more functional groups, the crosslinked structure becomes too dense due to the large number of NCO groups present in one molecule, resulting in no elasticity, brittleness, and no flexibility. Defects occur in the physical properties of the material and adhesive itself. There are also prepolymers derived from special alicyclic diisocyanate monomers, such as those shown in JP-A-52-141897 and JP-A-48-56789, but the majority of these are also trifunctional. However, even if a bifunctional polyisocyanate is obtained by reacting with a diol compound, the viscosity of the polyisocyanate itself without being diluted with a solvent is extremely high, exceeding 100,000 cps, making it practically impossible to use. There is. By the way, in the field of foam materials, adhesives, etc., in order to avoid the use of solvents, the viscosity of polyisocyanate as a hardening agent is set at 25℃.
It must be less than 5000cps. In addition, it is desirable that the NCO content of the polyisocyanate is high;
Generally, an NCO content of 12% by weight or more is required. On the other hand, when the aliphatic diisocyanate monomer itself is used, it is satisfactory in terms of the number of functional groups and viscosity, but as mentioned above, the vapor pressure of the diisocyanate monomer is high, so it is far from being practical in terms of its toxicity and irritation. Furthermore, when a bifunctional prepolymer with a high NCO content is produced using HMDI, which is industrially the most readily available aliphatic diisocyanate, free HMDI remaining in the prepolymer is purified to eliminate toxicity and irritation. The prepolymer obtained by
As described in JP-A No. 141297 and JP-A-48-56789, they usually have poor compatibility with solvents and other resins, and cannot be applied to the fields of foam materials and adhesives. Therefore, in the industry, it is used as a non-toxic, non-irritating foam material and adhesive because it is bifunctional, has low viscosity, has good compatibility with other resins, and does not substantially contain diisocyanate monomers. The emergence of a non-yellowing aliphatic liquid isocyanate suitable for the pharmaceutical field has been awaited. As a result of repeated research in view of these points, the present inventors surprisingly found that hexamethylene diisocyanate, which was conventionally said to have drawbacks in solubility in solvents and compatibility with resins, and A branched alkylene diol having a carbon number of 3 to 10 was selected from diols that were estimated to have the same effect as a raw material for a functional urethane prepolymer, and was reacted at an NCO/OH molar ratio of 8 or more to remove the excess. Hexamethylene diisocyanate content is 0.7% by weight or less, and 25
We have completed the present invention by discovering that an aliphatic urethane prepolymer with isocyanate at both terminals and having a viscosity of 5000 cps or less at °C can overcome the above problems. That is, the present invention provides hexamethylene diisocyanate, which is obtained by reacting hexamethylene diisocyanate with a branched alkylene diol having 3 to 10 carbon atoms at an NCO/OH molar ratio of 8 or more, and then purifying and removing excess hexamethylene diisocyanate. It is an aliphatic liquid bifunctional urethane prepolymer with isocyanate terminals at both terminals and has a diisocyanate content of 0.7% by weight or less and a viscosity at 25°C of 5000 cps or less. 3 to 10 carbon atoms with branching used in the present invention
The alkylene diol has a structure in which the main chain connecting both hydroxyl groups is not linear and has at least one side chain with 1 or more carbon atoms, and the main chain has an ether bond, an ester bond, etc. It may be included. Examples of these diols include, for example, 1.2
-propanediol, 1.2-butanediol, 2.3
-butanediol, 2-methyl-1,2-propanediol, 1.2-pentanediol, 2.3-pentanediol, 3-methyl-1,2-butanediol,
2-methyl 1,2-butanediol, 2-methyl-
2.3-butanediol, 2.3-dimethyl-2.3-butanediol, 2.4-pentanediol, 1.3-butanediol, 2-methyl-2.4-butanediol,
2-Methyl-2.4-pentanediol, 2.4-dimethyl-2.4-pentanediol, hexamethyltrimethylene glycol, neopentyl glycol, 2.2-dimethyl-1.3-butanediol, 2.2-
Dimethyl-1.3-pentanediol, 2.2.4-trimethyl-1.3-pentanediol, 1.4-pentanediol, 2methyl-2.5-pentanediol,
Examples include 3-methyl-2.5-pentanediol, 1.4-hexanediol, 2.5-hexanediol, 2.5-dimethyl-2.5-hexanediol, dipropylene glycol, 2.2-dimethyl-1.3-propanediol monohydroxybivalate, and the like. These may be used alone or in any combination. Particularly preferred among these diols is 1.3
-butanediol, neopentyl glycol. It is essential that the alkylene diol to be reacted with hexamethylene diisocyanate has a branch as described above. Unbranched diols, e.g. ethylene glycol, 1,3-propanediol, 1,4-
Butanediol, 1.5-pentanediol, 1.6-
Hexanediol, 1.7-heptanediol, 1.8
-octanediol, 1.9-nonanediol,
1.10-decanediol, diethylene glycol,
When using triethylene glycol, etc., the prepolymer that is the reaction product becomes solid and is extremely poorly soluble in general organic solvents. It is not practical because it is not compatible with acrylic polyol, and it is contrary to the purpose of the present invention. Furthermore, when a diol having 11 or more carbon atoms is used, the viscosity of the prepolymer similarly increases or becomes solid, and the NCO content of the resulting polymer becomes too low, which is not preferable. The reaction between hexamethylene diisocyanate and alkylene diol is carried out as follows. The reaction temperature ranges from room temperature to 200℃, preferably 100℃
The temperature range is from ℃ to 160℃. If the reaction temperature is low, it will take too long for the reaction to complete;
If the reaction temperature exceeds .degree. C., undesirable side reactions may occur, resulting in an increase in the viscosity of the prepolymer or significant coloring of the resulting prepolymer, making it impractical. During the reaction, any solvent that is inert to the isocyanate group may be used, and if necessary, a catalyst may be used to promote the reaction between the isocyanate group and the hydroxyl group. The molar ratio of hexamethylene diisocyanate and branched alkylene diol during the reaction is very important, and the viscosity at 25°C
Surprisingly, it was found that in order to obtain a polyisocyanate of 5000 cps or less, it was necessary to increase the NCO/OH molar ratio to 8 or more. NCO/OH when reacting conventional diisocyanate monomer and polyol
As shown in, for example, JP-A-52-141897, an equivalent ratio of 3 to 6 is preferred, and an equivalent ratio of 6 or more is said to be ineffective. However, the prepolymer of the present invention cannot achieve the objective of having a viscosity of 5000 cps or less at 25°C, as will be described later in Examples and Comparative Examples, when reacting with an NCO/OH molar ratio of 3 or 5, which has been conventionally considered suitable. It has become clear that this can only be achieved by increasing the molar ratio to 8 or more. On the other hand, if the reaction is carried out under conditions where the NCO/OH molar ratio exceeds 25, the amount of prepolymer produced per reaction is small and is not economical, so the NCO/OH molar ratio is selected in the range of 8 to 25. Things are good. When the reaction is completed, excess diisocyanate and solvent in the reaction mixture are recovered using, for example, a falling film evaporator or a solvent extraction method. This excess diisocyanate should be recovered as completely as possible, and the amount of diisocyanate monomer contained in the prepolymer should be
It is necessary to keep it below 0.7% by weight. This is because if more diisocyanate monomers are contained, problems such as toxicity and irritation arise due to the high vapor pressure of the diisocyanate monomers contained in the prepolymer. Although the prepolymer of the present invention is substantially free of HMDI, it has a high NCO
The white waxy solidification phenomenon seen with HMDI-based bifunctional prepolymers is not observed, and it is non-toxic and non-irritating, and the viscosity at 25℃ is less than 5000 cps, which is unprecedented for an aliphatic product. It is a non-yellowing bifunctional prepolymer with high NCO content and excellent compatibility with solvents and other resins, and can be applied to a wide range of fields such as foaming materials, adhesives, sealing materials, and flooring materials. This will be explained in more detail below with reference to Examples. Example 1 Hexamethylene diisocyanate (HMDI)
2520g and 142g of 1,2-propanediol to ethylene glycol monomethyl ether acetate 1260
Using g as a solvent, the reaction was carried out at 160°C for 1 hour. Unreacted HMDI and solvent were removed from the reaction solution using a thin film evaporator at 0.2 mmHg and 160°C. Viscosity at 25℃ as bottom liquid is 1500cpsNCO content 19.0
900 g of a liquid bifunctional prepolymer with a residual HMDI content of 0.5% by weight was obtained. Example 2 2520 g of HMDI and 104 g of neopentyl glycol were mixed at 120°C using 1260 g of trimethyl phosphate as a solvent.
The reaction was allowed to proceed for 1 hour. Purification was carried out in the same manner as in Example 1, and the viscosity at 25°C was 1300 cps and the NCO content
470 g of liquid prepolymer having a residual HMDI content of 18.8% by weight and 0.4% by weight was obtained. Example 3 2520 g of HMDI and 177 g of 2-methyl-2,4-pentanediol were reacted without a solvent at 160°C for 1 hour, and then purified in the same manner as in Example 1. The viscosity of the obtained prepolymer at 25°C was 1500 cps, NCO
The content is 16.9% by weight, and the residual HMDI is 0.4% by weight.
The yield was 580g. Example 4 2520 g of HMDI and 90 g of 2.3-butanediol were reacted without a solvent at 160°C for 1 hour. Purified in the same manner as in Example 1, with a viscosity of 2000 cps at 25°C and an NCO
420 g of prepolymer having a content of 19.0% by weight and a residual amount of HMDI of 0.3% by weight was obtained. Example 5 2520 g of HMDI and 182.5 g of 2.2.4-trimethyl-
700 g of 1.3-pentanediol and trimethyl phosphate
The mixture was reacted at 140° C. for 3 hours in a mixed solvent consisting of 700 g of ethylene glycol monomethyl ether acetate and 700 g of ethylene glycol monomethyl ether acetate. Purified in the same manner as in Example 1, with a viscosity of 2100 cps at 25°C, an NCO content of 17.0% by weight, and a residual
580 g of prepolymer containing 0.2% by weight of HMDI was obtained. Example 6 2520 g of HMDI and 90 g of 1,3-butanediol were reacted without a solvent at 160°C for 1 hour. Purification was carried out in the same manner as in Example 1, and the viscosity at 25°C was 700 cps.
430 g of prepolymer with an NCO content of 19.4% by weight and a residual HMDI content of 0.3% by weight was obtained. Example 7 The same operation as in Example 6 was carried out except that the amount of 1,3-butanediol was changed to 168 g, and the viscosity at 25°C was 2300 cps, the NCO content was 17.9% by weight, and the remaining
780 g of prepolymer containing 0.4% by weight of HMDI was obtained. Example 8 After reacting 2520 g of HMDI and 134 g of dipropylene glycol at 120°C for 3 hours without a solvent, purification was performed in the same manner as in Example 1, and the viscosity at 25°C was
1400cps, NCO content 17.6% by weight, residual HMDI amount 0.6
480 g of wt% prepolymer were obtained. Comparative Example 1 2520 g of HMDI and 62 g of ethylene glycol were reacted and purified in exactly the same manner as in Example 1, but the obtained product was a white waxy solid and did not become liquid even when heated to 50°C. Comparative Example 2 2520 g of HMDI and 76 g of 1,3-propanediol were reacted and purified in the same manner as in Example 8, but the product was a waxy solid at room temperature (25°C). Comparative Example 3 When 2520 g of HMDI and 90 g of 1.4-butanediol were reacted in the same manner as in Example 3, a precipitate was formed after the reaction, and the product after recovering unreacted monomers was a waxy solid that did not liquefy even at 50°C. . Comparative Example 4 2520 g of HMDI and 118 g of 1.6-hexanediol were reacted in the same manner as in Example 5, but a large amount of precipitate was produced after the reaction and the reaction could not be subjected to the purification step. The prepolymers obtained in Examples 1 to 8 described above are easily dissolved in organic solvents such as ethyl acetate, butyl acetate, toluene, xylene, and methyl ethyl ketone, and are also easily dissolved in polyester polyols,
Freely compatible with polyether polyols and polyacrylic polyols. On the other hand, the solid products obtained in Comparative Examples 1 to 3 hardly dissolved in organic solvents, and were not compatible with the above-mentioned polyols at all. Comparative Example 5 When 2520 g of HMDI and 240 g of 2.2-bis(4-hydroxycyclohexyl)propane were reacted and purified in the same manner as in Example 5, the obtained prepolymer had a viscosity of 78000 cps at 25°C and a viscosity of 1000 cps at 50°C. It was a highly viscous substance. Comparative Example 6 The same procedure as in Example 6 was performed except that the amount of 1,3-butanediol was changed to 450 g. The prepolymer obtained had a viscosity of 92000 cps at 25°C.
It was a highly viscous product with a viscosity of 14,000 cps at 50°C. Comparative Example 7 2520 g of HMDI and 270 g of 1,3-butanediol were reacted without a solvent at 160°C for 1 hour. When the generated reaction solution was analyzed as it was without being purified to remove unreacted HMDI as described in Example 1, the content of unreacted HMDI reached 58% by weight, indicating a strong
Due to the pungent odor of HMDI, a gas mask was required when handling it. When this product was purified in the same manner as in Example 1,
The viscosity of the obtained prepolymer at 25℃ is
It was 9000cps. Comparative Example 5 uses a diol having 15 carbon atoms, but the obtained prepolymer has a very high viscosity. In addition, in Comparative Example 6, the NCO/OH molar ratio of HMDI and 1.3-butanediol was 3, and in Comparative Example 7,
The NCO/OH molar ratio is 5. This comparative example, Example 6 (NCO/OH=15) and Example 7 (NCO/OH=15)
=8), in order to achieve the objective of the present invention, which is a viscosity of 5000 cps or less at 25°C,
It is also clear that the NCO/OH molar ratio needs to be 8 or more. Comparative Example 8 Reaction and purification was carried out in the same manner as in Example 6 except that 2520 g of HMDI was changed to 3330 g of IPDI. The obtained prepolymer was a resinous material with a viscosity of 100,000 cps or more at 25° C. and almost no fluidity. Comparative Example 9 2910 g of w,w' diisocyanate-1,3-dimethylcyclohexane (1.3-HXDI) and 90 g of 1.3-butanediol were reacted without a solvent at 160°C for 1 hour.
The obtained reaction solution was heated to 0.2 mmHg using a thin film distiller.
The product was purified by removing unreacted 1.3-H ₆ XDI at 160°C. The obtained prepolymer has a viscosity at 25℃.
It was 100,000 cps and was a resinous material with no fluidity. Hereinafter, in order to examine the usefulness of the various prepolymers obtained in Examples and Comparative Examples, preliminary tests for application of the RIM process were conducted, focusing on compatibility with polypropylene glycol, castability, and curing moldability. Reference example 1 Prepolymer obtained in Example 1 and molecular weight 3000
Polypropylene glycol with a hydroxyl value of 56
Blended so that the NCO/OH equivalent ratio was 1.0, and dibutyltin dilaurate was added as a catalyst to 0.1% of the total amount of the mixture.
After adding the weight percent, the mixture was stirred and mixed at 20°C. The resulting mixture was poured into a mold with an open top at 20°C.
The polyurethane resin was cured by heating at 80°C for 10 minutes. During stirring and mixing, the prepolymer and polypropylene glycol were easily and uniformly mixed at 20°C, and the resulting mixture was a colorless and transparent homogeneous liquid, which could be easily poured into a mold with an open top. The polyurethane resin obtained by heating and curing in a mold was transparent and colorless. Reference Examples 2 to 8 Using the prepolymers obtained in Examples 2 to 8,
A cast polyurethane resin was obtained in the same manner as in Reference Example 1.
The results are shown in Table 1. Reference Comparative Example 1 The same operation as in Reference Example 1 was performed except that the prepolymer obtained in Comparative Example 1 was used. When stirred and mixed at 20°C, the prepolymer was not compatible with polypropylene glycol at all, and existed only as lumps in the polypropylene glycol. Therefore, an attempt was made to heat the blend to 80°C and stir it further, but the prepolymer precipitated as particulate matter in the polypropylene glycol and was not compatible with the prepolymer. Pour this into a mold with an open top and heat at 80℃.
An attempt was made to cure it by heating it for 10 minutes, but the curing reaction did not proceed because the prepolymer and polypropylene glycol had phase-separated, making it impossible to mold the polyurethane resin. Reference Comparative Examples 2-3 The same operations as in Reference Example 1 were performed using the prepolymers obtained in Comparative Examples 2-3. The results were all the same as Reference Comparative Example 1, and the prepolymer was not compatible with polypropylene glycol, and it was impossible to mold the polyurethane resin. Reference Comparative Examples 4 to 6 The same operations as in Reference Example 1 were performed using the prepolymers obtained in Comparative Examples 5 to 7 of the present invention.
Because of the high viscosity of the prepolymers of Comparative Examples 5 to 7,
Stirring and mixing at 20°C was extremely difficult, and it was necessary to heat the mixture to 80°C. When heated to 80℃, the prepolymer and polypropylene glycol began to become compatible, but the curing reaction progressed during stirring at 80℃, and the mixture thickened into a gel before it became completely homogeneous, causing difficulty in filling the mold. Casting was impossible. Reference Comparative Example 7 The same operation as in Reference Example 1 was performed using the IPDI-based prepolymer obtained in Comparative Example 8 as the prepolymer. The prepolymer of Comparative Example 8 was a lump that showed almost no fluidity at room temperature, and it was impossible to mix and make it compatible with polypropylene glycol at 20°C. When this mixture was heated to 80℃ and stirred, the prepolymer and polypropylene glycol finally began to become compatible and homogeneous, but the curing reaction progressed during the heating and stirring, and the mixture was not completely homogeneous. It thickened and gelled, making it impossible to cast it into a mold. Reference Comparative Example 8 The same operation as in Reference Example 1 was performed except that the prepolymer obtained in Comparative Example 9 was used as the prepolymer. The results are exactly the same as Reference Comparative Example 7, and 20
Under conditions of 80°C, prepolymer and polypropylene glycol were not compatible, and under heating at 80°C, gelation occurred during stirring and mixing, making it impossible to obtain a polyurethane casting resin.

[Table] As is clear from Table 1, the prepolymer of the present invention has low viscosity and excellent compatibility with resins, so it has excellent mixing compatibility with polyol components such as polypropylene glycol at room temperature (20°C), and is excellent.
Demonstrates adaptability to the RIM process. Furthermore, the obtained polyurethane casting resin also showed appropriate elasticity and flexibility. On the other hand, the waxy solid prepolymers made of HMDI and non-branched diol obtained in Comparative Examples 1 to 3 are completely incompatible with polypropylene glycol and the curing reaction does not proceed, making it impossible to obtain polyurethane casting resin. Nakatsuta. Furthermore, the high viscosity prepolymers obtained in Comparative Examples 5 to 9 were also heated at room temperature (20°C).
Compatibility with polypropylene glycol was difficult and heating was required, but the viscosity increased and gelation occurred during heating, making it impossible to obtain a casting resin. In addition, a solvent-free two-component adhesive composition containing polypropylene glycol with a molecular weight of 1000 and a hydroxyl value of 170 as the main ingredient and the prepolymers obtained in the Examples and Comparative Examples of the present application as a curing agent was blended, and the composition was used to coat aluminum foil and polyethylene terephthalate film. The prepolymers obtained in Examples 1 to 8 were uniformly compatible with the main ingredient polypropylene glycol and gave adhesives with excellent flexibility, but the prepolymers obtained in Comparative Examples 1 to 3 The prepolymer is completely incompatible with polypropylene glycol and therefore does not function as an adhesive.
In addition, the prepolymers obtained in Comparative Examples 5 to 9 are also difficult to mix with the main ingredient and curing agent at room temperature (20°C).
It required heating to 80°C, making it impractical. Furthermore, those using the prepolymers obtained in Comparative Examples 8 and 9 had poor flexibility, and the adhesive layer cracked and peeled off when the adhered object was bent. As described above, a non-yellowing type bifunctional aliphatic compound that is substantially free of highly toxic diisocyanate monomers such as HMDI and IPDI and exhibits excellent adaptability to the RIM process field and the adhesive field. Liquid polyisocyanates have not been known in the past, and the polyisocyanates provided by the present invention are extremely useful industrially.

Claims (1)

[Claims] 1 Hexamethylene diisocyanate and a branched alkylene diol having 3 to 10 carbon atoms.
A double-terminated isocyanate with a hexamethylene diisocyanate content of 0.7% by weight or less and a viscosity of 5000 cps or less at 25°C, obtained by reacting at an NCO/OH molar ratio of 8 or more and purifying to remove excess hexamethylene diisocyanate. Aliphatic liquid urethane prepolymer.