JP3506399B2 - Method for producing polycarbodiimide resin powder - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a polycarbodiimide resin powder, and more specifically, a polycarbodiimide resin capable of obtaining a powder by a simple method without using an end-capping agent. The present invention relates to a method for producing powder.

[0002]

2. Description of the Related Art A polycarbodiimide resin is a polymer compound having a repeating unit of the formula --N.dbd.C.dbd.N--R--. Since this polycarbodiimide resin is excellent in heat resistance and the like,
It has been used for various purposes such as molding materials, resin modifiers and adhesives.

However, polycarbodiimide resins in general, and aromatic polycarbodiimide resins, which are particularly advantageous in terms of heat resistance and chemical resistance, are difficult to dissolve in various solvents, and when an attempt is made to increase the molecular weight, the reaction system gels, It is difficult to obtain a powder having excellent usability in the above various uses.

As a conventional technique relating to a method for producing a powder of a polycarbodiimide resin, for example, TW Campbell et al., J. Org. Chem., 28, 2069 (19)
63) CS Fold et al., Macromol. Syn., 1, 74 (1963) TW Campbell et al., Macromol. Syn., 3, 109 (196
9) and the like.These conventional techniques include producing a polycarbodiimide resin powder using a single solvent or a mixed solvent in which a raw material diisocyanate is dissolved and a generated polycarbodiimide resin is not dissolved. .

However, the polycarbodiimide resin powder obtained by precipitation in the above-mentioned prior art has a relatively low molecular weight and therefore has a large amount of residual isocyanate groups.
When handled at a temperature of 180 ° C or higher, the carbodiimidization reaction goes into a molten state again and the decarboxylation reaction occurs, causing foaming and swelling, which is a problem when used as a molding material or a modifier. ing.

TW Campbell et al., Macromol. S
yn., 3, 109 (1969) also shows findings on high molecular weight polycarbodiimide resins, but gelation occurred during the reaction, and this gel was crushed in a poor solvent and desolvated. Although a method of producing powder by using an experimental method is possible, it is not practical to use a crushing process of a gel and a desolvation process, or to use an excess amount of a poor solvent with respect to the gel. is not.

In order to improve these problems, J. Appl. P
olym. Sci., 21, 1999 (1977), Japanese Patent Publication No. 52-1675.
No. 9, JP-A-5-239223, etc.
Disclosed is a method of isolating a polycarbodiimide resin as a powder by reacting 4′-diphenylmethane diisocyanate with an organic monoisocyanate as a molecular weight regulator in an inert organic solvent in the presence of a carbodiimidization catalyst. .

That is, for the above J. Appl. Polym. Sci., The above reaction was carried out in a xylene solvent, and the solid precipitated while cooling to room temperature after completion of the reaction was isolated by filtration, while one of the filtrates was excessive. Was added to hexane, and the precipitated solid was isolated by filtration, and the powder obtained by drying the combined precipitate was called end-capped polycarbodiimide, and its characteristics are described. .

Further, Japanese Patent Publication No. 52-16759 described above is also the same as described above except that a mixed solvent of benzene / hexane is used as a synthetic solvent, as shown in Example 1 thereof.

Further, in the above-mentioned JP-A-5-239223, the above-mentioned carbodiimidization reaction is carried out by using a halogen-based solvent as a synthetic solvent to prepare a uniform polycarbodiimide resin solution, which is then cooled to form a slurry. A method for producing a powder having a narrow particle size distribution by spray-drying is described.The characteristics of these prior arts are to prevent gelation by controlling the molecular weight to a low level by using an endcapping agent, and It was to obtain a powder by precipitating a solid by utilizing the solubility of the polycarbodiimide resin.

[0011]

However, in the end-capped polycarbodiimide resin powder thus obtained by the prior art, reaction between end-capping agents occurs,
Since monocarbodiimide and low-molecular-weight carbodiimide are produced, they are decomposed and gasified depending on the application, and cause foaming, swelling, odor, etc., especially when an amine or the like is used as the terminal blocking agent, polycarbodiimide There is a problem that the heat resistance originally possessed by the resin is impaired.

When the end-capped polycarbodiimide resin powder is used in a medium, the medium may be deteriorated due to elution of low molecular weight substances into the medium. It has also been pointed out that isocyanates are generally expensive and their use has an unfavorable effect on costs.

The present invention solves the above-mentioned drawbacks of the prior art and provides a method for obtaining a polycarbodiimide resin having a high molecular weight simply and efficiently in the form of powder or granules without using an end-capping agent. Made for the purpose of providing.

[0014]

In order to solve the above-mentioned object, the constitution of the method for producing a polycarbodiimide resin powder adopted by the present invention is such that a polycarbodiimide resin is prepared from an organic diisocyanate in a solvent in the presence of a carbodiimidization catalyst. After synthesizing and cooling the resulting solution , polycarbodiimid
A method of obtaining a polycarbodiimide resin as a powder by precipitating a resin and making it into a slurry, wherein the organic diisocyanate has the formula (1)

[Chemical 4] (In the formula, R ₁ represents a hydrogen atom, a lower alkyl group or a lower alkoxy group), or a formula (2)

[Chemical 5] (In the formula, R ₂ and R ₃ represent a hydrogen atom, a lower alkyl group or a lower alkoxy group, and X represents an oxygen atom or a methylene group), or the formula (3)

[Chemical 6] (Wherein R ₄ and R ₅ represent a hydrogen atom, a lower alkyl group or a lower alkoxy group), and the solvent is an aliphatic hydrocarbon of 10 to 100 relative to 100 parts of an alicyclic ether. Parts, and using phospholene oxide as a carbodiimidization catalyst in an amount of 0.05% by weight or more based on the organic diisocyanate ,
Monomer concentration of organic diisocyanate at the start of reaction
Of 15% by weight to 70% by weight to carry out the reaction.
It is a characteristic.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.

The organic diisocyanate used in the present invention is first of the formula (1)

[Chemical 7] R _{1 in} the formula of this organic diisocyanate is a hydrogen atom, a lower alkyl group such as a methyl group, an ethyl group, a propyl group or a butyl group, or a lower alkyl group corresponding to the lower alkyl group. It represents an alkoxy group.

The organic diisocyanate used in the present invention has the formula (2)

[Chemical 8] And R ₂ and R _{3 in} the formula of the organic diisocyanate are the same hydrogen atom, lower alkyl group or lower alkoxy group as the above R _1, and
X represents an oxygen atom or a methylene group, respectively.

Further, the organic diisocyanate used in the present invention has the formula (3)

[Chemical 9] And R ₄ and R _{5 in} the formula of this organic diisocyanate represent the same hydrogen atom, lower alkyl group or lower alkoxy group as R ₁ .

A polycarbodiimide resin having crystallinity can be obtained from these organic diisocyanates. Specifically, as the organic diisocyanate represented by the above formula (1), p-phenylene diisocyanate,
Tolylene diisocyanate such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, 1-methoxyphenyl-2,
4-diisocyanate and the like, and organic diisocyanate represented by the above formula (2) include 4,4′-diphenylmethane diisocyanate, 4,4′-diphenyl ether diisocyanate and 3,3′-dimethyl-
4,4'-diphenyl ether diisocyanate,
Further, as the organic diisocyanate represented by the above formula (3), o-tolidine diisocyanate, 3,
Examples thereof include 3'-dimethoxy-4,4'-biphenyldiisocyanate. These organic diisocyanates can be used alone or as a mixture of two or more kinds. For example, as a mixture with the 4,4′-diphenylmethane diisocyanate, tolylene diisocyanate can be mentioned as a preferable example. .

The above organic diisocyanate becomes a polycarbodiimide resin by a carbodiimidization reaction in a solvent. In the present invention, this carbodiimidization reaction is carried out in a mixed solvent in which an alicyclic ether and an aliphatic hydrocarbon are mixed. Thus, although the reason is not clear, the production of by-product uretonimine is prevented.

Examples of the alicyclic ether in the above mixed solvent include tetrahydrofuran, dioxane, tetrahydropyran, etc. Among them, tetrahydrofuran (hereinafter abbreviated as THF) has the highest effect of suppressing the formation of uretonimine. It is preferable in that respect.

As the aliphatic hydrocarbon in the above mixed solvent, pentane, hexane or heptane can be exemplified. Other than these, it cannot be used, but they are liquid at room temperature and thus easy to handle. Further, when THF is used as the alicyclic ether, it has a boiling point close to that of the alicyclic ether, so that it can be easily recovered by distillation. The recovered product can be reused as it is, and the powder can be easily dried. The advantage of is obtained.

When an aromatic hydrocarbon is used instead of an aliphatic hydrocarbon, uretonimine is conspicuously produced, and the reaction cannot proceed sufficiently.

It is necessary that the mixing (volume) ratio of the aliphatic hydrocarbon / alicyclic ether is 0.1 ≦ mixing ratio ≦ 1.0, preferably 0.25 ≦ mixing ratio ≦ 0.75. ,
If the mixing ratio is lower than 0.1, the solvent solubility is too high and precipitation does not occur easily, and desolvation from the precipitated powder becomes extremely poor. Conversely, if the mixing ratio is higher than 1.0, Since the reaction cannot be fully dissolved in a low molecular weight state where the reaction has not progressed sufficiently, phase separation in the system occurs at an early stage,
The reaction becomes difficult to control.

Regarding the amount of the organic diisocyanate in the mixed solvent, it is necessary that the monomer concentration of the organic diisocyanate at the start of the reaction is 15% by weight to 70% by weight, preferably 25% by weight to 50% by weight. When the concentration is lower than 15% by weight, precipitation is unlikely to occur in this case as well, so that there is little merit in considering the production efficiency. On the contrary, from the viewpoint of production efficiency, the higher the monomer concentration, the better. However, if it is too high, the solution viscosity at the time of reaction becomes too high, and it becomes difficult to stir the solution.

The carbodiimidization reaction of the above organic diisocyanate is carried out in the presence of a carbodiimidization catalyst. As this carbodiimidization catalyst, any conventionally known one can be used without any problem, for example, 3
-Methyl-1-phenyl-2-phosphorene-1-oxide, 3-methyl-1-phenyl-3-phosphorene-1-
Examples thereof include phospholene oxides such as oxide and 1-ethyl-2-phospholen-1-oxide, and among them, 3-methyl-1-phenyl-2-phospholen-1-oxide is preferable from the viewpoint of reactivity.

The amount of catalyst used in the carbodiimidization reaction also correlates with the amount of uretonimine produced, and in the case of using phospholene oxides such as 3-methyl-1-phenyl-2-phospholene-1-oxide, the reaction It is desirable to use the catalyst in an amount of 0.05% by weight or more, preferably 0.1 to 1.0% by weight, based on the organic diisocyanate used at the time of initiation, and increasing the concentration of the catalyst adversely affects the cost. Not only that, but when it is higher than 1.0% by weight, the polymerization reaction rate becomes too fast and the reaction becomes extremely difficult to control.

On the contrary, the amount of phospholene oxides as a carbodiimidization catalyst is 0.0 with respect to the organic diisocyanate.
If it is less than 5% by weight, the production rate of uretonimine increases, which is not preferable. That is, the greater the amount of uretonimine produced, the easier the reaction system is to form a gel before producing the powder, and the greater the amount of uretonimine in the produced powder, the more likely it is that foaming will occur depending on the application. The range becomes extremely narrow.

The reaction temperature in the production method of the present invention is determined by the kind of solvent used in the mixed solvent, and when there are differences in the boiling points of the plurality of solvents used, it is between the highest boiling point and the lowest boiling point. It becomes the temperature, and when it is azeotropic, it becomes the azeotropic temperature. The reaction time, which varies depending on the reaction temperature, is about several hours to 10 hours.

In the present invention, after synthesizing the polycarbodiimide resin in this way, it is cooled and
The polycarbodiimide resin can be obtained as a powder or granules by precipitating the bodiimide resin and making it into a slurry, and the cooling is performed when the number average molecular weight reaches 3000 or more (preferably 4500 or more). All you have to do is to get a particle size of 1
The carbodiimide resin can be obtained as a powder or granules of 0 to 300 μm.

This timing is based on the NCO of the reaction mixture.
% Or IR spectrum, and the theoretical value of NCO% when the number average molecular weight exceeds a predetermined value (for example, 2% or less if the raw material is MDI), or IR spectrum carbodiimide group transmittance / isocyanate group transmittance It may be determined by determining whether the theoretical value of (5 or more for MDI) has been reached.

[0032]

EXAMPLES The present invention will now be described in more detail by way of examples.

Example 1 A 500 ml four-necked flask equipped with a Dimroth condenser, a thermometer, and a mechanical stirrer was prepared as a synthesizer, and 122.5 g of 4,4'-diphenylmethane diisocyanate and THF and hexane were introduced from a raw material inlet. 10
196.0 g of the solution mixed at 0:25 (volume ratio) was added, and the mixture was heated and stirred. When the solution temperature exceeded 40 ° C, 0.2% by weight of 3-methyl-1-phenyl-2-phospholen-1-oxide was added to the raw material isocyanate, and the mixture was stirred under reflux to about 3%. Reaction was carried out for 5 hours (the molecular weight at this point was 5500 on average).
degree).

After completion of heating, the flask was immersed in an ice bath for cooling, the liquid temperature was lowered to about 5 ° C., and the temperature was maintained for 5 hours. As a result, a white powder broke out from the reaction solution and became a slurry state. This slurry is
5 mm nutche and No. When the filter paper of No. 2 was used and vacuum filtration was performed using an aspirator, the filtration was completed in several tens of seconds. The solid content thus obtained was dried by heating under reduced pressure to obtain a white powder in a yield of 90% or more.

Example 2 The same synthesis apparatus as in Example 1 was used.
95.8 g of 4'-diphenylmethane diisocyanate,
16.7 g of 80-tolylene diisocyanate and THF
227.5 g of a solvent prepared by mixing hexane and hexane at 100: 50 (volume ratio) was added, and the mixture was heated and stirred. Solution temperature is 4
When the temperature exceeds 0 ° C, it is 0.2 with respect to the raw material isocyanate.
Wt% 3-methyl-1-phenyl-2-phosphorene-
After adding 1-oxide, the reaction was performed under reflux for 2.5 hours (the molecular weight at this point was 620 in number average).
0).

After heating, cooling was carried out with stirring in the same manner as in Example 1, and the state was maintained for 10 hours. As a result, a white powder was deposited and turned into a slurry state. This slurry was filtered under reduced pressure using a Nutsche in the same manner as in Example 1, and dried by heating under reduced pressure to obtain a white powder in a yield of 90% or more.

Example 3 Using the same synthesizer as in Example 1, the raw material charging port
15 'g of 4'-diphenylmethane diisocyanate
Then, 150.0 g of a solvent in which THF and hexane were mixed at 100: 25 (volume ratio) was added, and the mixture was heated and stirred. When the solution temperature exceeded 40 ° C., 0.2% by weight of 3-methyl-1-phenyl-2-phospholen-1-oxide was added to the raw material isocyanate, and then reacted under reflux for 3.6 hours. Was carried out (the molecular weight at this point is about 6200 in number average).

After completion of heating, cooling was performed while continuing stirring as in Example 1, and the state was maintained for 1 hour. As a result, a white powder was deposited in a slurry state with poor fluidity. By subjecting this slurry to heat drying under reduced pressure, a white powder was obtained in a yield of 90% or more.

Example 4 The same synthesis apparatus as in Example 1 was used, and from the raw material charging port 4,
122.5 g of 4'-diphenylmethane diisocyanate
Then, 208.5 g of a solvent prepared by mixing THF and heptane at a volume ratio of 100: 50 was added, and the mixture was heated and stirred. When the solution temperature exceeded 40 ° C., 0.2% by weight of 3-methyl-1-phenyl-2-phospholen-1-oxide was added to the raw material isocyanate, and the mixture was reacted for 5.2 hours under reflux. Was carried out (the molecular weight at this point is about 6200 in number average).

After completion of heating, cooling was carried out while continuing stirring as in Example 1, and the state was maintained for 5 hours. As a result, white powder was deposited and the solution was slurried. This slurry was suction filtered using a Nutsche in the same manner as in Example 1, and dried by heating under reduced pressure to obtain a white powder in a yield of 90% or more.

Example 5 Using the same synthesizing apparatus as in Example 1, from the raw material charging port 4,
200.0 g of a solvent prepared by mixing 50.0 g of 4′-diphenylmethane diisocyanate and THF and hexane at a ratio of 100: 35 (volume ratio) was added, and the mixture was heated and stirred. When the solution temperature exceeded 40 ° C, 0.2% by weight of 3-methyl-1-phenyl-2-phospholen-1-oxide was added to the raw material isocyanate, and then the reaction was performed for 8 hours under reflux. It was

After completion of heating, cooling was carried out while continuing stirring as in Example 1, and the state was maintained for 5 hours. As a result, white powder was deposited and the solution was slurried. This slurry was suction filtered using a Nutsche in the same manner as in Example 1, and dried by heating under reduced pressure to obtain a white powder in a yield of 90% or more.

COMPARATIVE EXAMPLE 1 Using the same synthesizer as in Example 1, from the raw material charging port 4,
95.7 g of 4'-diphenylmethane diisocyanate and 170 g of THF were added and the mixture was heated and stirred. When the solution temperature exceeded 40 ° C, 0.03% by weight of 3-methyl-1-phenyl-2-phospholen-1-oxide was added to the raw material isocyanate, and then the reaction was performed for 10 hours under reflux. As a result, the viscosity of the solution was increased to a spinnable state, after which the solution gelled. The gel was dried and pulverized to prepare a sample for comparison experiment.

Comparative Example 2 Using the same synthesizer as in Example 1, from the raw material charging port 4,
4'-diphenylmethane diisocyanate 95.7 g and a mixed solution of toluene and THF in a volume ratio of 1: 1 168.
9 g was added and the mixture was heated and stirred. When the solution temperature exceeds 40 ° C, 0.2% by weight based on the raw material isocyanate
When 3-methyl-1-phenyl-2-phosphorene-1 oxide was added and reacted under reflux for 2.7 hours, the solution gelled. The gel was dried and pulverized to prepare a sample for comparison experiment.

COMPARATIVE EXAMPLE 3 Using the same synthesizer as in Example 1, from the raw material charging port 4,
30.0 g of 4′-diphenylmethane diisocyanate and 270.0 g of hexane were immersed, and the mixture was heated and stirred.
When the solution temperature exceeded 40 ° C., 0.2% by weight of 3-methyl-1-phenyl-2-based on the raw material isocyanate was used.
After adding phosphorene-1-oxide, the reaction was carried out under reflux for 5.5 hours. Precipitation of solids (lumps) on the wall surface of the reaction vessel during heating caused the concentration of solids in the solution to decrease, and powder could not be obtained. Further, the precipitate (comparative experimental sample) was confirmed by IR and thermal analysis to have a low molecular weight.

COMPARATIVE EXAMPLE 4 Using the same synthesizer as in Example 1, from the raw material charging port 4,
225.0 g of a solvent prepared by mixing 25.0 g of 4′-diphenylmethane diisocyanate and 100: 20 (volume ratio) of THF and hexane was added, and the mixture was heated and stirred. When the solution temperature exceeded 40 ° C, 0.2% by weight of 3-methyl-1-phenyl-2-phospholen-1-oxide was added to the raw material isocyanate, and then the reaction was performed for 16 hours under reflux. It was After completion of heating, stirring is continued as in Example 1 so that cooling is performed for 100 hours, and further 5 ° C.
The state was maintained for 100 hours, but although the degree of cloudiness of the solution increased, powder precipitation did not occur, and a lump was precipitated. The solution was rewashed with a large excess of hexane,
The obtained solid material was dried and pulverized to obtain a sample for comparison experiment.

Comparative Example 5 Using the same synthesizer as in Example 1, from the raw material charging port 4,
4'-diphenylmethane diisocyanate 105.0 g
195.0 g of a solvent obtained by mixing THF and hexane at a volume ratio of 100: 200 was added, and the mixture was heated and stirred.
When the solution temperature exceeded 40 ° C., 0.2% by weight of 3-methyl-1-phenyl-2-based on the raw material isocyanate was used.
After adding phosphorene-1-oxide, the reaction was carried out under reflux for 4 hours. During the heating reaction, a solid (gel-like) portion and a solvent portion were clearly separated. After the reaction, cooling was carried out while continuing stirring in the same manner as in Example 1, but the solid content (lump) was deposited on the wall surface or the stirring blade, and was precipitated.
It could not be obtained in a powdered state. The obtained precipitate was dried and pulverized to obtain a sample for comparative experiments.

<Comparative Experiment> Examples 1 to 5 and Comparative Example 1
Thermal evaluation of the powders and solids obtained in ~ 5 was conducted as follows. The results are shown in Table 1. 300 ° C weight reduction rate 300 at the time of TG measurement at a temperature rising rate of 20 ° C / min.
The value of the weight reduction rate at the time when the temperature reached ℃ was calculated from the TG curve.
Molded under the condition of 0 minutes and made into a film, 260 ° C
It was left on the plate surface for 10 minutes and the presence or absence of foaming was visually confirmed.

[0048]

[Table 1]

[0049]

INDUSTRIAL APPLICABILITY The method for producing a polycarbodiimide resin powder of the present invention is produced by producing a polycarbodiimide resin from only an organic diisocyanate in the presence of a carbodiimidization catalyst in a solvent without using an end capping agent. It is a method of obtaining a polycarbodiimide resin as a powder.

In the present invention, by using a mixed solvent in which an alicyclic ether and an aliphatic hydrocarbon are mixed in a volume ratio of 100: 10 to 100 as the solvent, a carbodiimide having a high molecular weight can be obtained without forming uretonimine. The powder can be obtained by a simple method such as filtration.

Further, the polycarbodiimide resin powder obtained by the production method of the present invention has excellent properties such that foaming does not occur at all when it is placed at a high temperature.

Continuation of the front page (56) Reference JP-A-8-208789 (JP, A) JP-A-7-330913 (JP, A) JP-A-2-202906 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) C08G 18/00-18/87

Claims (4)

(57) [Claims] 1. A polycarbodiimide resin is synthesized from an organic diisocyanate in a solvent in the presence of a carbodiimidization catalyst, and the resulting solution is cooled to obtain a polycarbodiimide.
A method for obtaining a polycarbodiimide resin as a powder by precipitating a resin and making it into a slurry, wherein an organic diisocyanate represented by the formula (1): (In the formula, R ₁ represents a hydrogen atom, a lower alkyl group or a lower alkoxy group), or a compound represented by the formula (2): (Wherein R ₂ and R ₃ represent a hydrogen atom, a lower alkyl group or a lower alkoxy group, and X represents an oxygen atom or a methylene group), or a compound represented by the formula (3): (Wherein R ₄ and R ₅ represent a hydrogen atom, a lower alkyl group or a lower alkoxy group), and the solvent is an aliphatic hydrocarbon of 10 to 100 relative to 100 parts of alicyclic ether. Part of the organic diisocyanate is used at a concentration of 0.05% by weight or more based on the organic diisocyanate as the carbodiimidization catalyst.
The method for producing a polycarbodiimide resin powder, characterized in that the reaction is carried out at a rate of 15% by weight to 70% by weight . 2. The alicyclic ether used in the mixed solvent is
The method for producing a polycarbodiimide resin powder according to claim 1, which is tetrahydrofuran. 3. The method for producing a polycarbodiimide resin powder according to claim 1, wherein the aliphatic hydrocarbon solvent used as the mixed solvent is pentane, hexane or heptane. 4. The method for producing a polycarbodiimide resin powder according to claim 1, wherein the precipitated polycarbodiimide resin powder has a particle size of 10 to 300 μm.