# Patent

## Title
Anionic water-soluble polymer precipitation in salt solution

## Abstract

A hydrolysis stabilizer for an ester group-containing resin, which comprises as a main component a carbodiimide having at least two carbodiimide groups in the molecule and resulting from 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate or a mixture of 4,4'-dicyclohexylmethane diisocyanate and isophorone diisocyanate, or from a mixture of tetramethylxylylene diisocyanate with 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate or a mixture of 4,4'-dicyclohexylmethane diisocyanate and isophorone diisocyanate; and a process for the hydrolysis stabilization of an ester group-containing resin, which comprises mixing a polyester type resin with the above hydrolysis stabilizer.

## Background
1. Field of the Invention

The present invention relates to a hydrolysis stabilizer for an ester group-containing resin and a process for the hydrolysis stabilization of an ester group-containing resin using said hydrolysis stabilizer. More particularly, it relates to a hydrolysis stabilizer for an ester group-containing resin which stabilizer does not generate a bad odor when kneaded with the resin at a high temperature, has an excellent compatibility and reactivity with a resin to which the stabilizer is added, even at a low temperature and exhibits thereby an excellent hydrolysis stabilizing effect and comprises a carbodiimide as a main component, and to a process for the hydrolysis stabilization of an ester group-containing resin using the above hydrolysis stabilizer.

2. Description of Related Art

Ester group-containing resins (referred to hereinafter as ester type resins in some cases), for example, polyester polyurethane (PU), polyethylene terephthalate (PET), polybutylene terephthalate (PBT) and the like have excellent elasticity and moldability, and hence, have been employed in various uses.

However, for example, the above-mentioned polyester polyurethane resin is usually obtained by urethanizing a diisocyanate such as 4,4'-diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI) or the like with a difunctional polyester polyol, so that it has many ester groups in the molecule. Accordingly, it is known that there are such problems that not only is this ester group easily hydrolyzed with moisture to cause reduction of molecular weight, but also the acidic carboxyl group formed by this hydrolysis accelerates the hydrolysis of the ester linkage, so that the strength is reduced and the reduction of strength makes it impossible for the resin per se to resist the strain caused during the curing of the resin, whereby cracking and further reduction of strength are caused.

In order to prevent such deterioration of physical properties, it has been tried to add various additives during the molding of a polyester polyurethane resin to trap the carboxyl groups and alcohol groups formed by the hydrolysis, thereby preventing hydrolysis from further proceeding.

The above additives include, for example, oxazolines, epoxy compounds, aromatic polycarbodiimides, aliphatic monocarbodiimides and the like. These additives are usually in the form of powder and used in such a manner that they are dry blended with resin pellets or mixed in a given amount with the resin by use of a measuring hopper during molding or spinning, and then, the resulting mixture is melt-kneaded at a given temperature (250.degree.-300.degree. C. in the case of polyethylene terephthalate).

However, the above-mentioned epoxy compounds and oxazolines have no sufficient effect of improving the hydrolysis resistance, increase the melt viscosity of the resin and deteriorate the moldability, so that they have no practical usability. Moreover, the above aromatic carbodiimides are usually thermosetting, and hence, their carbodiimide groups cross-link upon heating and when they are kneaded with the resin, the viscosity of the resulting mixture increases or they become lump-like and are ununiformly dispersed in the resin, and hence, in some cases, no desirable effect of hydrolysis stabilization can be obtained.

For the purpose of preventing the above-mentioned problems of aromatic carbodiimides when heated, there have been developed various aromatic carbodiimides having a group of high steric hindrance in the ortho-position to the carbodiimide group. However, these aromatic carbodiimides are pyrolyzed by a heat applied when they are melt-kneaded with a polyester polyurethane resin, and in addition, generate remarkably unpleasant odor due to the vaporization of impurities or starting materials, resulting in a deterioration of working atmosphere. Furthermore, the gas generated contains aromatic amines and the like and hence is very dangerous in view of not only bad odor but also toxicity, and hence, there is such a problem that a large scale deodorizing or ventilating apparatus becomes necessary.

Moreover, as aliphatic carbodiimides, the use of dicyclohexylcarbodiimide is well known; however, this dicyclohexylcarbodiimide reacts easily with water to be converted to dicyclohexylurea, and hence, has a problem in that close attention must be paid for preventing moisture in the storage of dicyclohexylcarbodiimide. Therefore, it is inadequate to use in industry. Furthermore, a monocarbodiimide is a low molecular weight compound and when added to a polyester polyurethane resin, it bleeds out of the resin, so that it has such a problem that the hydrolysis resistance is not sufficient.

It is an object of the present invention to overcome the above disadvantages of the prior art and provide a hydrolysis stabilizer for an ester group-containing resin such as polyester polyurethane resin or the like which stabilizer has an excellent compatibility with said resin, can be easily added without any trouble to said resin during the synthesis and melt-kneading of said resin, has a high molecular weight and, therefore, can sufficiently exhibit the effect of hydrolysis stabilization of the said resin.

It is another object of the present invention to provide a process for the hydrolysis stabilizer of an ester group-containing resin using the above hydrolysis stabilizer.

According to the present invention, there is provided a hydrolysis stabilizer for an ester group-containing resin, which comprises as a main component a carbodiimide having at least two carbodiimide groups in the molecule and resulting from 4,4'-dicyclohexylmethane diisocyanate represented by the formula (I): ##STR1## or isophorone diisocyanate represented by the formula (II): ##STR2## or a mixture of 4,4'-dicyclohexylmethane diisocyanate of the formula (I) with isophorone diisocyanate of the formula (II), or, a carbodiimide having at least two carbodiimide groups in the molecule and resulting from a mixture of tetramethylxylylene diisocyanate represented by the formula (III): ##STR3## with 4,4'-dicyclohexylmethane diisocyanate represented by the formula (I), isophorone diisocyanate represented by the formula (II) or a mixture of 4,4'-dicyclohexylmethane diisocyanate of the formula (I) and isophorone diisocyanate of the formula (II).

According to the present invention, there is further provided a process for the hydrolysis stabilization of an ester group-containing resin which comprises mixing a polyester resin with a carbodiimide having at least two carbodiimide groups in the molecule and resulting from 4,4'-dicyclohexylmethane diisocyanate represented by the formula (I): ##STR4## or isophorone diisocyanate represented by the formula (II): ##STR5## or a mixture of 4,4'-dicyclohexylmethane diisocyanate of the formula (I) with isophorone diisocyanate of the formula (II), or, a carbodiimide having at least two carbodiimide groups in the molecule and resulting from a mixture of tetramethylxylylene diisocyanate represented by the formula (III): ##STR6## with 4,4'-dicyclohexylmethane diisocyanate represented by the formula (I), isophorone diisocyanate represented by the formula (II) or a mixture of 4,4'-dicyclohexylmethane diisocyanate of the formula (I) and isophorone diisocyanate of the formula (II).

The present hydrolysis stabilizer for an ester group-containing resin comprises as a main component: and resulting from 4,4'-dicyclohexylmethane diisocyanate represented by the above formula (I) (referred to hereinafter as HMDI in some cases), or, isophorone diisocyanate represented by the above formula (II) (referred to hereinafter as IPDI in some cases), or, a mixture of HMDI and IPDI, or and resulting from a mixture of tetramethylxylylene diisocyanate represented by the above formula (III) (referred to hereinafter as TMXDI in some cases) with HMDI, IPDI or a mixture of HMDI and IPDI. Said carbodiimide can be produced by subjecting (1) HMDI, IPDI or a mixture of HMDI and IPDI, or (2) a mixture of TMXDI with HMDI, IPDI or a mixture of HMDI and IPDI, as the starting materials to carbodiimidization reaction accompanied by decarboxylation reaction.

The above carbodiimidization reaction is effected in the presence of a suitable carbodiimidization catalyst, and as the carbodiimidization catalyst which can be used, organic phosphorus compounds are preferable, and phosphorene oxides are particularly preferable in view of activity. Specifically, there are mentioned 3-methyl-1-phenyl-2-phosphorene-1-oxide, 3-methyl-1-ethyl-2-phosphorene-1-oxide, 1,3-dimethyl-2-phosphorene -1-oxide, 1-phenyl-2-phosphorene-1-oxide, 1-ethyl-2-phosphorene-1-oxide, 1-methyl-2-phosphorene-1-oxide and double bond isomers thereof. Among them, 3-methyl-1-phenyl-2-phosphorene-1-oxide, which is easily commercially available, is particularly preferable.

The above carbodiimidization reaction can be carried out by a known method, for example, by adding the above-mentioned catalyst to (1) HMDI, IPDI or a mixture of HMDI and IPDI, or (2) a mixture of TMXDI with HMDI, IPDI or a mixture of HMDI and IPDI in the absence of a solvent or to a solution of (1) or (2) in a solvent inert thereto, in a proportion of 0.1 to 10% by weight (a larger amount is possible when the economy is neglected), preferably 0.5 to 5% by weight, based on the total weight of the isocyanates in the atmosphere of an inert gas such as nitrogen or the like or with bubbling of the inert gas, and then heating the resulting mixture with stirring at a reaction temperature within the range of from 150.degree. C. to 200.degree. C., thereby allowing a carbodiimidization reaction accompanied by decarboxylation reaction to proceed.

The reaction time for the above reaction is varied depending upon the reaction temperature, the kind and amount of the catalyst and the like, and when, for example, HMDI is used as the starting material and 3-methyl-1-phenyl-2-phosphorene-1-oxide is added in a proportion of 1% by weight based on the total weight of the isocyanates and the reaction is effected at a reaction temperature of 180.degree. C., it is possible to obtain in about 20 hours a carbodiimide compound resulting from HMDI, and even when IPDI is used as the starting material the same applies.

When, for example, a mixture of TMXDI and HMDI is used as the starting material, it is possible to obtain a carbodiimide compound resulting from the mixture of TMXDI and HMDI similarly to the above.

Incidentally, the proceeding of the reaction may be confirmed by observing the absorption of isocyanate group at 2258 cm.sup.-1 in an infrared absorption spectrum or confirmed by a titration method.

In the above reaction, when (1) HMDI, IPDI or a mixture of HMDI and IPDI, or (2) a mixture of TMXDI with HMDI, IPDI or a mixture of HMDI and IPDI is used, a carbodiimide represented by the following formula (IV) can be obtained:

wherein R.sub.1 and R.sub.2 may be the same as or different from each other and each represents the residue of TMXDI, HMDI or IPDI freed from NCO group; and the polymerization style of the above isocyanates may be a random polymerization or a block polymerization; and n is an integer of 2 or more.

As the carbodiimide which is the main component of the present hydrolysis stabilizer for an ester group-containing resin, there may be a product obtained by end-blocking a carbodiimide having terminal isocyanate groups obtained by the above-mentioned method, with an amine, a carboxylic acid, an acid anhydride, a monoisocyanate or the like.

When the terminal isocyanate of the carbodiimide is blocked with a monoisocyanate, a carbodiimide represented by the following formula (V) can be obtained:

wherein R.sub.3 and R.sub.4 may be the same as or different from each other and each represents the residue of the monoisocyanate freed from NCO group; m is an integer of 1 or more; and R.sub.5 represents the residue of the diisocyanate used in the reaction similarly to R.sub.1 and R.sub.2.

Incidentally, the proportion (mole ratio) of the diisocyanate (1) HMDI, IPDI or a mixture of HMDI and IPDI or (2) a mixture of TMXDI with HMDI, IPDI or a mixture of HMDI and IPDI! to the monoisocyanate is 1:2-302:, preferably 4:2-19:2, and when the diisocyanate and the monoisocyanate are used in a proportion of 3:2, the number of carbodiimide units in one molecule, namely n, becomes 4 and when the proportion is 19:2, n becomes 20.

When the terminals of the carbodiimide are blocked with the monoisocyanate, it is favorable, for obtaining a carbodiimide having the desired molecular weight, that the diisocyanate and the monoisocyanate are previously mixed to effect carbodiimidization, because it is possible to control the amount of the monocarbodiimide produced by condensation of the monoisocyanate molecules with each other.

The monoisocyanate used for blocking the terminals of the carbodiimide includes n-butyl isocyanate, tert-butyl isocyanate, isobutyl isocyanate, ethyl isocyanate, n-propyl isocyanate, cyclohexyl isocyanate, n-octyl isocyanate and the like, and these may be used alone or in admixture of two or more.

Moreover, when the terminals of a carbodiimide are blocked with a monofunctional compound having a group capable of reacting with the isocyanate group, for example, an amine, a carboxylic acid or an acid anhydride, a carbodiimide represented by the formula (VI) can be obtained:

wherein R.sub.6 and R.sub.7 may be the same as or different from each other and each represents the residue of the monofunctional compound having a group capable of reacting with an isocyanate group, for example, an amine, a carboxylic acid or an acid anhydride, formed by reaction with the isocyanate; x represents a bond formed by the reaction of the monofunctional compound having a group capable of reacting with the isocyanate group with the isocyanate; and p is an integer of 2 or more.

When the terminals of a carbodiimide are blocked with a monofunctional compound having a group capable of reacting with an isocyanate group, for example, an amine, a carboxylic acid or an acid anhydride, the reaction between the isocyanate and the end-blocking agent may be effected before the carbodiimidization or may be effected after the carbodiimidization to a suitable degree of polymerization by adding the end-blocking agent in an amount equivalent to the residual isocyanate.

The present hydrolysis stabilizer for an ester group-containing resin comprises the above-mentioned carbodiimide as a main component, and in the actual use, the above carbodiimide may be used as a single component or may be used in combination with an appropriate adjuvant.

The present process for the hydrolysis stabilization of an ester group-containing resin comprises mixing the above-mentioned carbodiimide with the ester type resin. The mixing method is not critical and any appropriate mixing method can be adopted.

The proportion of the above carbodiimide to the ester group-containing resin is 0.01 to 5% by weight, preferably 0.3 to 1% by weight, and when the proportion is less than 0.01% by weight, the amount of the carbodiimide bond for the ester group becomes small, the hydrolysis stabilization effect cannot be said to be sufficient. When the proportion exceeds 5% by weight, the carbodiimide exhibits its plasticizing effect on the ester group-containing resin and adversely affects the physical properties of the resin.

Incidentally, as carbodiimides having particularly preferable hydrolysis resistance, there can be mentioned carbodiimides having a degree of polymerization of 5 to 30 obtained from HMDI and a monoisocyanate, for example, cyclohexyl isocyanate; end-blocked carbodiimides having a degree of polymerization of 5 to 30 obtained from HMDI and an amine, for example, cyclohexylamine; carbodiimides having a degree of polymerization of 5 to 30 derived from a mixture of HMDI: TMXDI=10:1-1:10 and end-blocked with a monoisocyanate such as cyclohexyl isocyanate or the like or an amine such as cyclohexylamine or the like; etc.

JP-A-07-017939 discloses isocyanate-terminated carbodiimides having a degree of polymerization (n) of 0 to 10 and an improved compatibility. However, this isocyanate is low in reactivity owing to steric hindrance and when the carbodiimide is mixed with the ester group-containing resin, the reaction of the isocyanate with the carboxyl or hydroxyl group present at the ends of the ester group-containing resin is slow and the isocyanate remains as such in the ester group-containing resin even after the melt-kneading. Therefore, there is such a problem that this isocyanate reacts with moisture to generate carbon dioxide, whereby voids and the like are formed in the ester group-containing resin.

On the other hand, in the case of the present hydrolysis stabilizer for an ester group-containing resin, the reactivity of the terminal isocyanate group of the carbodiimide resulting from HMDI, IPDI or a mixture of HMDI and IPDI which is the main component of the hydrolysis stabilizer, is sufficiently high even when the carbodiimide results from a mixture of TMXDI with HMDI, IPDI or a mixture of HMDI and IPDI. When the carbodiimide is melt-kneaded with the ester group-containing resin, the terminal isocyanate groups are consumed by the reaction with the carboxyl or hydroxyl group present at the ends of the ester group-containing resin, and there is substantially no case where the isocyanate remains as such in the ester group-containing resin after the melt-kneading. Therefore, there is no problem of voids and the like due to carbon dioxide.

Furthermore, JP-A-07-017939 discloses carbodiimides in which the terminal isocyanates are blocked with an alcohol or an amine. However, as described above, this carbodiimide is low in reactivity because of steric hindrance, and in order to obtain the desired hydrolysis stabilizing effect, it is necessary that the carbodiimide be added in an amount as large as possible within the limited addition amount range (when the amount of the carbodiimide added is too large, there appears a plasticizing effect on the ester group-containing resin). Accordingly, the blocking of the terminal isocyanate group with an alcohol or an amine results in an increase of molecular weight and also a decrease of the above-mentioned addition amount, and hence, is not desirable in view of the hydrolysis stabilizing effect.

On the other hand, in the case of the present hydrolysis stabilizer for an ester group-containing resin, the reactivity of the terminal isocyanate group of the carbodiimide which is the main component of the stabilizer, is sufficiently high as described above, and hence, even when the terminal isocyanate group is blocked with an alcohol or an amine to increase the molecular weight, a sufficient hydrolysis stabilizing effect is exhibited without increasing the addition amount so much.

Examples are shown below to explain the present invention in more detail.

Synthesis of carbodiimides

To 300 g of HMDI was added, as a carbodiimidization catalyst, 1.5 g of 3-methyl-1-phenyl-2-phosphorene-1-oxide (referred to hereinafter as carbodiimidization catalyst), and they were subjected to a condensation reaction at 180.degree. C. for 10 hours in a nitrogen atmosphere to obtain a carbodiimide resulting from HMDI (degree of polymerization=3).

The same procedure as in Synthesis Example 1 was repeated, except that the reaction time was changed as shown in Table 1 to obtain carbodiimides as shown in Table 1. ______________________________________ Reaction time Polymerization Synthesis Example (hr)       degree ______________________________________ 2              15         10 3              27         20 4              35         30 ______________________________________

To 300 g of HMDI was added 1.5 g of the carbodiimidization catalyst and they were subjected to a reaction at 185.degree. C. for 5 hours while nitrogen was bubbled thereinto, to obtain a carbodiimide resulting from HMDI (degree of polymerization =10).

The same procedure as in Synthesis Example 1 was repeated, except that the reaction time was changed as shown in Table 2 to obtain carbodiimides shown in Table 2. ______________________________________ Reaction time Polymerization Synthesis Example (hr)       degree ______________________________________ 6              16         10 7              28         20 8              38         30 ______________________________________

To a mixture of 236 g of HMDI with 25.0 g of cyclohexyl isocyanate (referred to hereinafter as CHI) was added 2.60 g of the carbodiimidization catalyst, and they were subjected to a reaction at 185.degree. C. for 19 hours while nitrogen was bubbled thereinto, to obtain a carbodiimide resulting from HMDI and CHI (degree of polymerization=10).

The starting materials and the reaction conditions were changed as shown in Table 3 to obtain carbodiimides shown CHI means a cyclohexyl isocyanate. ______________________________________ Synthesis Example 10      11       12   13    14 ______________________________________ Diisocyanate HMDI    HMDI     IPDI IPDI  IPDI Amount (g)   498     760      200  400   622 Monoisocyanate CHI     CHI      CHI  CHI   CHI Amount (g)   25      25       25   25    25 Catalyst amount (g) 5.2     7.8      2.3  4.3   6.2 Reaction time (hr) 20      48       21   27    52 Polymerization degree 20      30       10   20    30 ______________________________________

To 288 g of HMDI was added 20 g of cyclohexylamine and they were stirred at 100.degree. C. for one hour while nitrogen was bubbled thereinto and subsequently 2.9 g of the carbodiimidization catalyst was added thereto, after which the resulting mixture was subjected to a reaction at 185.degree. C. for 30 hours, to obtain a carbodiimide resulting from HMDI and having terminal urea bonds (degree of polymerization=10).

The end-blocking agent was changed to an alcohol, an amine, a carboxylic acid or an acid anhydride as shown in Tables 4, 5 and 6, and in the same manner as in Synthesis Example 13, there were obtained carbodiimides having a urea bond, a urethane bond, an imido bond or an amido bond in the molecular chain as shown in Tables 4, 5 and 6. ______________________________________ Synthesis Example 16      17     18   19      20 ______________________________________ Diisocyanate HMDI    IPDI   IPDI HMDI    HMDI Amount (g)   498     245    467  288     498 Blocking agent Cyclo-  Do.    Do.  Cyclohexyl- Do. hexyl-              carboxylic amine               acid Amount (g)   20      20     20   26      26 Catalyst amount (g) 5.5     2.5    4.7  2.9     5.5 Reaction time (hr) 52      30     50   32      48 Polymerization degree 20      10     20   10      20 ______________________________________ ______________________________________ Synthesis Example 21      22      23    24    25 ______________________________________ Diisocyanate HMDI    HMDI    HMDI  HMDI  HMDI Amount (g)   288     498     288   498   288 Blocking agent Phthalic Do.     Ben-  Do.   Dibutyl- anhy-           zoic        amine dride           acid Amount (g)   30      30      24    24    26 Catalyst amount (g) 2.9     5.5     2.9   5.5   2.9 Reaction time (hr) 35      52      31    50    32 Polymerization degree 10      20      10    20    10 ______________________________________ ______________________________________ Synthesis Example 26      27       28    29    30 ______________________________________ Diisocyanate HMDI    IPDI     IPDI  IPDI  IPDI Amount (g)   498     245      467   245   467 Blocking agent Di-     Cyclohe- Do.   Phthalic Do. butyl-  xyl-           anhy- amine   carboxy-       dride lic acid Amount (g)   26      26       26    30    30 Catalyst amount (g) 5.5     2.5      4.7   2.5   4.7 Reaction time (hr) 48      30       50    30    50 Polymerization degree 20      10       20    10    20 ______________________________________

A polybutylene terephthalate PBT! manufactured by DAINIPPON INK & CHEMICALS INC. (Product No. BT-1000) was melt-kneaded with 1% by weight of the present hydrolysis stabilizer for an ester group-containing resin which comprised as the main component one of the carbodiimides obtained in Synthesis Examples 1 to 30, by means of a twin screw extruder and injection molded into JIS-K6301 Dumbbell No. 4. The sample thus obtained was immersed in hot water at 95.degree. C. and the tensile strength of the sample was measured by a tensile tester every time shown in Table 7. The results are shown in Tables 7 to 9 incidentally, in Tables 7 to 9, the numerals in the uppermost section refer to Synthesis Example Nos. in which the carbodiimide was synthesized, and the term "blank" means a sample in which no present hydrolysis stabilizer for an ester group-containing resin was used (the same applies hereinafter)!. __________________________________________________________________________ t/day blank 1  2   3  4   5  6   7  8   9 __________________________________________________________________________ 0 610 610 610 610 620 610 610 610 610 610 10 410 520 540 540 540 520 530 530 540 570 15 250 400 420 430 430 400 420 420 420 460 20 150 200 230 230 230 190 220 230 230 260 30 100 150 170 170 170 140 170 170 170 190 (Kg/cm.sup.2) __________________________________________________________________________ __________________________________________________________________________ t/day 10  11 12  13 14  15 16  17 18  19 __________________________________________________________________________ 0 610 620 610 610 610 610 610 610 610 610 10 580 590 560 570 570 580 580 560 560 560 15 470 480 450 460 460 470 470 450 450 450 20 260 270 250 260 260 260 270 250 250 240 30 200 200 190 190 200 200 200 180 190 170 (Kg/cm.sup.2) __________________________________________________________________________ __________________________________________________________________________ t/day 20 21  22 23 24 25 26 27 28  29 30 __________________________________________________________________________ 0 610 610 610 610 610 600 600 610 600 610 610 10 560 560 570 560 560 570 570 550 560 560 560 15 450 450 450 450 450 460 460 440 450 440 450 20 250 250 250 240 250 260 270 240 240 240 250 30 180 180 180 170 180 190 200 170 170 170 170 (Kg/cm.sup.2) __________________________________________________________________________

To a urethane elastomer manufactured by Nisshinbo Industries, Inc. (Reference No. F-30) was added 1% by weight of the present hydrolysis stabilizer for an ester group-containing resin comprising as the main component one of the carbodiimides in Synthesis Examples 1 to 30, and the resulting mixture was molded into a film by a cast method, after which the film was punched to JIS-K6301 Dumbbell No. 4. The sample thus obtained was immersed in hot water at 95.degree. C. and the tensile strength of the sample was measured by a tensile tester every time shown in Tables 10 to 12. The results are shown in Tables Table 10 to 12. __________________________________________________________________________ t/day blank 1  2   3  4   5  6   7  8   9 __________________________________________________________________________ 0 870 880 880 890 890 870 880 880 880 870 3 520 650 660 660 660 640 650 650 660 710 7 140 570 580 590 590 560 570 570 570 590 10 --  510 520 530 530 500 510 500 510 530 15 --  190 200 200 200 110 110 200 210 210 (Kg/cm.sup.2) __________________________________________________________________________ __________________________________________________________________________ t/day 10 11  12 13 14 15 16 17 18  19 20 __________________________________________________________________________ 0 880 880 880 880 880 870 870 870 870 870 870 3 710 720 710 710 710 710 710 700 700 710 710 7 600 600 590 590 600 350 350 320 350 580 580 10 530 530 520 540 540 320 340 300 310 500 500 15 240 250 200 190 200 110 130 100 120 190 200 (Kg/cm.sup.2) __________________________________________________________________________ __________________________________________________________________________ t/day 21  22 23  24 25  26 27  28 29  30 __________________________________________________________________________ 0 870 870 870 870 880 880 870 870 870 870 3 700 710 710 710 710 720 670 670 670 640 7 560 570 570 570 570 580 530 550 540 550 10 500 510 500 510 510 510 470 480 510 510 15 180 190 170 180 170 180 140 170 170 180 (Kg/cm.sup.2) __________________________________________________________________________ --: destructed

A polybutylene terephthalate PBT! elastomer manufactured by DAINIPPON INK & CHEMICALS, INC. (Product No. GRILUX registered trademark! EH-700) and 0.5% by weight of the present hydrolysis stabilizer for an ester group-containing resin comprising as the main component one of the carbodiimides obtained in Synthesis Examples 1 to 30 were melt-mixed and extruded using a twin screw extruder and then formed into a film of about 500 .mu.m using a T-die, after which the film thus obtained was injection molded into JIS-K6301 Dumbbell No. 4. The sample thus obtained was immersed in hot water at 95.degree. C. and the tensile strength was measured by a tensile tester every time shown in Tables 13 to 15. The results are shown in Tables 13 to 15. __________________________________________________________________________ t/day blank 1   2  3  4  5  6  7  8   9  10 __________________________________________________________________________ 0 350 350 350 350 350 350 350 350 350 350 350 10 330 350 350 350 350 340 340 340 350 350 350 15 310 340 350 350 350 330 340 340 340 350 350 20 290 320 330 340 340 320 330 340 340 350 350 30 220 320 330 330 340 310 320 330 330 340 340 (Kg/cm.sup.2) __________________________________________________________________________ __________________________________________________________________________ t/day 11 12  13 14 15 16 17 18 19  20 21 __________________________________________________________________________ 0 350 350 350 350 350 350 350 350 350 350 350 10 350 350 350 350 350 350 350 350 340 340 340 15 350 350 350 350 350 350 350 340 340 340 340 20 350 340 340 340 350 350 340 340 330 330 320 30 340 330 340 340 340 340 330 330 320 320 310 (Kg/cm.sup.2) __________________________________________________________________________ ______________________________________ t/day 22     23     24   25   26   27   28   29   30 ______________________________________ 0    350    350    350  350  350  350  350  350  350 10    340    340    340  350  350  340  340  340  340 15    340    330    330  340  340  330  330  320  330 20    320    310    320  330  340  320  320  310  310 30    310    300    310  320  320  300  300  300  300 (Kg/cm.sup.2) ______________________________________

A polyethylene terephthalate PET! resin manufactured by KANEBO LTD. (Product No. EFG-7) and 0.5% by weight of the present hydrolysis stabilizer for an ester group-containing resin comprising as the main component one of the carbodiimides obtained in Synthesis Examples 1 to 30 were melt-mixed and extruded using a twin screw extruder and then formed into a film of about 500 .mu.m using a T-die, after which the film thus obtained was injection molded into JIS-K6301 Dumbbell No. 4. The sample thus obtained was immersed in hot water at 95.degree. C. and the tensile strength was measured by a tensile tester every time shown in Tables 16 to 18. The results are shown in Tables 16 to 18. __________________________________________________________________________ t/day blank 1   2  3  4  5  6  7  8   9  10 __________________________________________________________________________ 0 630 630 630 630 630 630 630 630 630 630 630 10 640 650 650 640 650 650 650 650 650 650 640 30 590 650 650 650 650 650 650 650 650 650 650 60 460 630 640 640 640 620 630 640 640 650 650 (Kg/cm.sup.2) __________________________________________________________________________ __________________________________________________________________________ t/day 11 12  13 14 15 16 17 18 19  20 21 __________________________________________________________________________ 0 630 630 630 630 630 630 630 630 630 630 630 10 650 640 650 650 650 650 650 650 650 650 650 30 650 650 650 650 650 650 650 650 650 650 650 60 650 620 630 630 640 650 620 620 600 600 600 (Kg/cm.sup.2) __________________________________________________________________________ ______________________________________ t/day 22     23     24   25   26   27   28   29   30 ______________________________________ 0    630    630    630  630  630  630  630  630  630 10    650    650    650  650  650  650  650  650  650 30    650    650    650  650  650  650  650  650  650 60    620    600    600  640  640  600  600  600  600 (Kg/cm.sup.2) ______________________________________

Synthesis of carbodiimides

To one of the diisocyanate mixtures shown in Tables 19 and 20 was added 1.5% by weight, based on the total weight of the isocyanates, of the carbodiimidization catalyst and the resulting mixture was heated at 185.degree. C. to be subjected to a reaction until the degree of polymerization (n) became 10. ______________________________________ Synthesis Example  31      32      33    34    35    36 ______________________________________ Diisocyanate HMDI    HMDI    HMDI  IPDI  IPDI  IPDI Amount (g) 65.5    131.0   196.5 55.6  111.1 166.7 TMXDI   TMXDI   TMXDI TMXDI TMXDI TMXDI 183.0   122.0   61.0  183.0 122.0 61.0 Monoiso- Not     Not     Not   Not   Not   Not cyanate  used    used    used  used  used  used Catalyst 3.7     3.8     3.9   3.6   3.5   3.4 amount (g) Reaction 30      25      20    30    26    20 time (hr) Polymerization 10      10      10    10    10    10 degree ______________________________________ ______________________________________ Synthesis Example 37         38      39 ______________________________________ Diisocyanate  HMDI       HMDI    HMDI Amount (g)    65.5       131.0   196.5 IPDI       IPDI    IPDI 166.7      111.1   55.6 Monoisocyanate Not        Not     Not used       used    used Catalyst amount (g) 3.5        3.6     3.8 Reaction time (hr) 20         19      19 Polymerization degree 10         10      10 ______________________________________

To one of the mixtures shown in Tables 21 and 22 was added cyclohexyl isocyanate so that the degree of polymerization (n) becomes 10 (diisocyanate:monoisocyanate=9:2 by mole), and the carbodiimidization catalyst was added in a proportion of 1.5% by weight based on the total weight of the isocyanates, after which the resulting mixture was heated at 185.degree. C. to be subjected to a reaction until the peak of the isocyanate disappeared in the infrared absorption (IR) spectrum. ______________________________________ Synthesis Example 40         41      42 ______________________________________ Diisocyanate  HMDI       HMDI    HMDI Amount (g)    65.5       131.0   196.5 TMXDI      TMXDI   TMXDI 183.0      122.0   61.0 Monoisocyanate Cyclo-     Cyclo-  Cyclo- hexyl      hexyl   hexyl isocya-    isocya- isocya- nate       nate    nate Amount (g)    27.8       27.8    27.8 Catalyst amount (g) 4.1        4.2     4.3 Reaction time (hr) 28         24      19 Polymerization degree 10         10      10 ______________________________________ ______________________________________ Synthesis Example  43      44      45    46    47    48 ______________________________________ Diisocyanate IPDI    IPDI    IPDI  HMDI  HMDI  HMDI Amount (g) 55.6    111.1   166.7 65.5  131.0 196.5 TMXDI   TMXDI   TMXDI IPDI  IPDI  IPDI 183.0   122.0   61.0  166.7 111.1 55.6 Monoiso- Cyclo-  Cyclo-  Cyclo- Cyclo- Cyclo- Cyclo- cyanate  hexyl   hexyl   hexyl hexyl hexyl hexyl isocy-  isocy-  isocy- isocy- isocy- isocy- anate   anate   anate anate anate anate Amount (g) 27.8    27.8    27.8  27.8  27.8  27.8 Catalyst 4.0     3.9     3.8   3.5   3.6   3.8 amount (g) Reaction time 30      25      20    21    20    20 (hr) Polymerization 10      10      10    10    10    10 degree ______________________________________

To one of the mixtures shown in Tables 23 and 24 was added cyclohexylamine so that the degree of polymerization (n) became 10 (diisocyanate:amine=11:2 by mole), and the carbodiimidization catalyst was added in a proportion of 1.5% by weight based on the total weight of the isocyanates, after which the resulting mixture was heated at 185.degree. C. to be subjected to a reaction until the peak of the isocyanate disappeared in IR. ______________________________________ Synthesis Example  49      50      51    52    53    54 ______________________________________ Diisocyanate HMDI    HMDI    HMDI  IPDI  IPDI  IPDI Amount (g) 65.5    131.0   196.5 55.6  111.1 166.7 TMXDI   TMXDI   TMXDI TMXDI TMXDI TMXDI 183.0   122.0   61.0  183.0 122.0 61.0 Amine    Cyclo-  Cyclo-  Cyclo- Cyclo- Cyclo- Cyclo- hexyl   hexyl   hexyl hexyl hexyl hexyl amine   amine   amine amine amine amine Amount (g) 22.0    22.0    22.0  22.0  22.0  22.0 Catalyst 3.7     3.8     3.9   3.6   3.5   3.4 amount (g) Reaction 29      25      19    30    25    20 time (hr) Polymerization 9       9       9     9     9     9 degree ______________________________________ ______________________________________ Synthesis Example 55         56      57 ______________________________________ Diisocyanate  HMDI       HMDI    HMDI Amount (g)    65.5       131.3   196.5 IPDI       IPDI    IPDI 166.7      111.1   55.6 Amine         Cyclo-     Cyclo-  Cyclo- hexyl      hexyl   hexyl amine      amine   amine Amount (g)    22.0       22.0    22.0 Catalyst amount (g) 3.5        3.6     3.8 Reaction time (hr) 19         22      20 Polymerization degree 9          9       9 ______________________________________

To one of the mixtures shown in Tables 25 and 26 was added cyclohexyl isocyanate so that the degree of polymerization (n) became 20 (diisocyanate:monoisocyanate=19:2 by mole) and the carbodiimidization catalyst was added in a proportion of 1.5% by weight based on the total weight of the isocyanates, after which the resulting mixture was heated at 185.degree. C. to be subjected to a reaction until the peak of the isocyanate disappeared in IR. ______________________________________ Synthesis Example 58         59      60 ______________________________________ Diisocyanate  HMDI       HMDI    HMDI Amount (g)    65.5       131.0   196.5 TMXDI      TMXDI   TMXDI 183.0      122.0   61.0 Cyclo-     Cyclo-  Cyclo- Monoisocyanate hexyl      hexyl   hexyl isocy-     isocy-  isocy- anate      anate   anate Amount (g)    13.2       13.2    13.2 Catalyst amount (g) 3.9        4.0     4.1 Reaction time (hr) 30         24      21 Polymerization degree 20         20      20 ______________________________________ ______________________________________ Synthesis Example  61      62      63    64    65    66 ______________________________________ Diisocyanate IPDI    IPDI    IPDI  HMDI  HMDI  HMDI Amount (g) 55.6    111.1   166.7 65.5  131.0 196.5 TMXDI   TMXDI   ThXDI IPDI  IPDI  IPDI 183.0   122.0   61.0  166.7 111.1 55.6 Monoiso- Cyclo-  Cyclo-  Cyclo- Cyclo- Cyclo- Cyclo- cyanate  hexyl   hexyl   hexyl hexyl hexyl hexyl isocy-  isocy-  isocy- isocy- isocy- isocy- anate   anate   anate anate anate anate Amount (g) 13.2    13.2    13.2  13.2  13.2  13.2 Catalyst 3.8     3.7     3.6   3.7   3.8   4.0 amount (g) Reaction 29      24      20    23    19    20 time (hr) Polymerization 20      20      20    20    20    20 degree ______________________________________

To one of the mixtures shown in Tables 27 and 28 was added cyclohexylamine so that the degree of polymerization (n) became 20 (diisocyanate: amine=21:2 by mole), and the carbodiimidization catalyst was added in a proportion of 1.5% by weight based on the total weight of the isocyanates, after which the resulting mixture was heated at 185.degree. C. to be subjected to a reaction until the peak of the isocyanate disappeared in IR. ______________________________________ Synthesis Example  67      68      69    70    71    72 ______________________________________ Diisocyanate HMDI    HMDI    HMDI  IPDI  IPDI  IPDI Amount (g) 65.5    131.0   196.5 55.6  111.1 166.7 TMXDI   TMXDI   TMXDI TMXDI TMXDI TMXDI 183.0   122.0   61.0  183.0 122.0 61.0 Amine    Cyclo-  Cyclo-  Cyclo- Cyclo- Cyclo- Cyclo- Amount (g) hexyl   hexyl   hexyl hexyl hexyl hexyl amine   amine   amine amine amine amine 10.4    10.4    10.4  10.4  10.4  10.4 Catalyst  3.7     3.8     3.9   3.6   3.5   3.4 amount (g) Reaction time 52      50      48    51    50    50 (hr) Polymerization 19      19      19    19    19    19 degree ______________________________________ ______________________________________ Synthesis Example 73         74      75 ______________________________________ Diisocyanate  HMDI       HMDI    HMDI Amount (g)    65.5       131.0   196.5 IPDI       IPDI    IPDI 166.7      111.1   55.6 Amine         Cyclo-     Cyclo-  Cyclo- Amount (g)    hexyl      hexyl   hexyl amine      amine   amine 10.4       10.4    10.4 Catalyst amount (g) 3.5        3.6     3.8 Reaction time (hr) 47         48      48 Polymerization degree 19         19      19 ______________________________________

To one of the mixtures shown in Tables 29 and 30 was added cyclohexylcarboxylic acid so that the degree of polymerization (n) became 9 (diisocyanate:cyclohexylcarboxylic acid=10:2 by mole), and the carbodiimidization catalyst was added in a proportion of 1.5% by weight based on the total weight of the isocyanates, after which the resulting mixture was heated at 185.degree. C. to be subjected to a reaction until the peak of the isocyanate disappeared in IR. ______________________________________ Synthesis Example 76         77       78 ______________________________________ Diisocyanate  HMDI       HMDI     HMDI Amount (g)    65.5       131.0    196.5 TMXDI      TMXDI    TMXDI 183.0      122.0    61.0 Carboxylic acid Cyclo-     Cyclo-   Cyclo- Amount (g)    hexyl      hexyl    hexyl carboxylic carboxylic carboxylic acid       acid     acid 28.5       28.5     28.5 Catalyst amount (g) 3.7        3.8      3.9 Reaction time (hr) 30         25       20 Polymerization degree 9          9        9 ______________________________________ ______________________________________ Synthesis Example  79      80      81    82    83    84 ______________________________________ Diisocyanate IPDI    IPDI    IPDI  HMDI  HMDI  HMDI Amount (g) 55.6    111.1   166.7 65.5  131.0 196.5 TMXDI   TMXDI   TMXDI IPDI  IPDI  IPDI 183.0   122.0   61.0  166.7 111.1 55.6 Carboxylic Cyclo-  Cyclo-  Cyclo- Cyclo- Cyclo- Cyclo- acid     hexyl   hexyl   hexyl hexyl hexyl hexyl Amount (g) carbox- carbox- carbox- carbox- carbox- carbox- ylic    ylic    ylic  ylic  ylic  ylic acid    acid    acid  acid  acid  acid 28.5    28.5    28.5  28.5  28.5  28.5 Catalyst  3.6     3.5     3.4   3.5   3.6   3.8 amount (g) Reaction time 30      26      20    20    19    19 (hr) Polymerization 9       9       9     9     9     9 degree ______________________________________

To one of the mixtures shown in Tables 31 and 32 was added phthalic anhydride so that the degree of polymerization (n) became 9 (diisocyanate:phthalic anhydride=10:2 by mole), and the carbodiimidization catalyst was added in a proportion of 1.5% by weight based on the total weight of the isocyanates, after which the resulting mixture was heated at 185.degree. C. to be subjected to a reaction until the peak of the isocyanate disappeared in IR. ______________________________________ Synthesis Example  85      86      87    88    89    90 ______________________________________ Diisocyanate HMDI    HMDI    HMDI  IPDI  IPDI  IPDI Amount (g) 65.5    131.0   196.5 55.6  111.1 166.7 TMXDI   TMXDI   TMXDI TMXDI TMXDI TMXDI 183.0   122.0   61.0  183.0 122.0 61.0 Acid anhydride Phthalic Phthalic Phthalic Phthalic Phthalic Phthalic Amount (g) anhy-   anhy-   anhy- anhy- anhy- anhy- dride   dride   dride dride dride dride 32.9    32.9    32.9  32.9  32.9  32.9 Catalyst  3.7     3.8     3.9   3.6   3.5   3.4 amount (g) Reaction time 28      24      19    30    25    20 (hr) Polymerization 9       9       9     9     9     9 degree ______________________________________ ______________________________________ Synthesis Example 90         91       92 ______________________________________ Diisocyanate  HMDI       HMDI     HMDI Amount (g)    65.5       131.0    196.5 IPDI       IPDI     IPDI 166.7      111.1    55.6 Acid anhydride Phthalic   Phthalic Phthalic Amount (g)    anhydride  anhydride anhydride 32.9       32.9     32.9 Catalyst amount (g) 3.5        3.6      3.8 Reaction time (hr) 21         20       20 Polymerization degree 9          9        9 ______________________________________

A polybutylene terephthalate PBT! manufactured by DAINIPPON INK & CHEMICALS, INC. (Product No. BT-1000) and 1% by weight of the present hydrolysis stabilizer for an ester group-containing resin comprising as the main component one of the carbodiimides obtained in Synthesis Examples 31 to 92 were melt-kneaded using a twin screw extruder and then injection molded into JIS-K6301 Dumbbell No. 4. The sample thus obtained was immersed in hot water at 95.degree. C. and the tensile strength was measured by a tensile tester every time shown in Tables 33 to 38. The results are shown in Tables 33 to 38. __________________________________________________________________________ t/day 31 32  33 34 35 36 37 38 39  40 41 __________________________________________________________________________ 0 610 620 620 610 620 620 620 620 620 620 620 10 540 550 540 540 530 530 540 530 520 570 580 15 410 420 420 420 430 420 430 420 430 450 460 20 230 240 230 250 240 240 230 230 240 250 260 30 180 170 180 170 170 180 180 180 170 180 190 (Kg/cm.sup.2) __________________________________________________________________________ __________________________________________________________________________ t/day 42 43  44 45 46 47 48 49 50  51 52 __________________________________________________________________________ 0 610 610 610 610 620 610 620 610 610 620 610 10 580 590 570 580 570 590 590 530 560 540 540 15 470 470 480 470 460 470 480 430 440 420 420 20 270 270 460 270 250 270 280 240 250 250 240 30 190 180 190 200 190 180 180 170 180 180 170 (Kg/cm.sup.2) __________________________________________________________________________ __________________________________________________________________________ t/day 53 54  55 56 57  58 59 60 61  62 63 __________________________________________________________________________ 0 610 620 610 620 610 610 610 610 620 610 610 10 560 540 530 540 560 560 570 580 570 590 590 15 440 420 450 450 440 470 480 470 460 470 470 20 250 250 240 240 230 270 260 270 250 270 270 30 180 180 180 170 170 180 190 200 190 180 180 (Kg/cm.sup.2) __________________________________________________________________________ __________________________________________________________________________ t/day 64 65  66 67 68  69 70 71 72  73 74 __________________________________________________________________________ 0 610 610 610 620 610 620 610 610 620 610 620 10 570 680 570 540 530 540 560 590 540 530 540 15 480 470 480 420 450 450 440 470 420 450 450 20 260 260 260 250 240 240 230 270 250 240 240 30 190 180 190 180 180 170 170 180 180 180 170 (Kg/cm.sup.2) __________________________________________________________________________ __________________________________________________________________________ t/day 75 76  77 78 79  80 81 82 83  84 85 __________________________________________________________________________ 0 610 600 610 610 600 610 600 610 600 610 600 10 570 520 520 530 530 530 520 530 520 520 530 15 470 420 430 430 440 430 430 420 430 430 430 20 250 220 230 210 220 230 230 240 230 230 230 30 180 130 140 130 140 150 150 130 140 140 140 (Kg/cm.sup.2) __________________________________________________________________________ ______________________________________ t/day 86      87      88    89    90    91    92 ______________________________________ 0   610     600     610   610   610   610   610 10   530     530     520   530   530   520   520 15   440     430     430   440   430   430   440 20   220     230     230   220   230   230   240 30   140     150     150   140   150   150   150 (Kg/cm.sup.2) ______________________________________

To a urethane elastomer manufactured by Nisshinbo Industries Inc. (Product No. F-30) was added 1% by weight of the present hydrolysis stabilizer for an ester group-containing resin comprising as the main component one of the carbodiimides obtained in Synthesis Examples 31 to 92 and then the resulting mixture was formed into a film by a cast method, after which the film was punched to obtain JIS-K6301 Dumbbell No. 4. The sample thus obtained was immersed in hot water at 95.degree. C. and the tensile strength was measured by a tensile tester every time shown in Tables 39 to 44. The results are shown in Tables 39 to 44. __________________________________________________________________________ t/day 31 32  33 34 35  36 37 38 39  40 41 __________________________________________________________________________ 0 890 890 880 880 870 880 890 880 890 890 880 3 650 640 650 670 650 640 650 640 650 710 700 7 580 590 590 580 600 590 580 590 580 600 600 10 530 530 540 530 520 520 510 520 520 530 510 15 180 170 160 150 160 170 160 150 140 200 210 (Kg/cm.sup.2) __________________________________________________________________________ __________________________________________________________________________ t/day 42 43  44 45 46  47 48 49 50  51 52 __________________________________________________________________________ 0 870 870 870 860 870 860 880 870 870 870 880 3 680 690 670 680 690 700 680 650 640 650 650 7 600 590 580 570 580 590 580 600 590 580 590 10 510 510 500 480 500 500 490 520 520 510 540 15 210 190 200 210 200 210 200 160 170 160 160 (Kg/cm.sup.2) __________________________________________________________________________ __________________________________________________________________________ t/day 53 54  55 56 57  58 59 60 61  62 63 __________________________________________________________________________ 0 870 880 890 880 890 870 870 870 870 860 870 3 640 650 670 650 650 670 680 690 670 680 690 7 590 580 590 600 590 580 600 590 580 570 580 16 520 510 520 520 540 500 510 510 500 480 500 15 170 160 150 160 170 200 210 190 200 210 200 (Kg/cm.sup.2) __________________________________________________________________________ __________________________________________________________________________ t/day 64 65  66 67 68  69 70 71 72  73 74 __________________________________________________________________________ 0 860 860 890 870 860 890 890 880 890 890 890 3 700 680 650 670 680 650 650 650 670 650 650 7 590 570 590 600 580 590 590 580 590 590 590 10 500 480 540 490 500 540 540 510 520 540 540 15 210 210 170 170 180 170 170 160 150 180 170 (Kg/cm.sup.2) __________________________________________________________________________ __________________________________________________________________________ t/day 75 76  77 78 79  80 81 82 83  84 85 __________________________________________________________________________ 0 860 860 890 870 860 890 880 890 870 860 890 3 680 680 650 670 680 650 650 650 670 680 650 7 580 570 590 600 580 590 580 590 600 580 590 10 500 480 540 490 500 540 510 540 490 500 540 15 180 210 170 170 180 170 160 170 170 180 170 (Kg/cm.sup.2) __________________________________________________________________________ ______________________________________ t/day 86      87      88    89    90    91    92 ______________________________________ 0   860     890     890   870   860   890   890 3   680     650     650   670   680   650   650 7   570     590     590   600   580   590   590 10   480     540     540   490   500   540   540 15   210     170     170   170   180   170   170 ______________________________________ (Kg/cm.sup.2) ______________________________________

To a polybutylene terephthalate PBT! elastomer manufactured by DAINIPPON INK & CHEMICALS, INC. (Product No. GRILUX registered trademark! EH-700) was added 0.5% by weight of the present hydrolysis stabilizer for an ester group-containing resin comprising as the main component one of the carbodiimides obtained in Synthesis Examples 31 to 92 and the resulting mixture was melt-mixed and extruded using a twin screw extruder and then formed into a film of about 500 .mu.m using a T-die, after which the film thus obtained was injection molded to obtain JIS-K6301 Dumbbell No. 4. The sample thus obtained was immersed in hot water at 95.degree. C. and the tensile strength was measured by a tensile tester every time shown in Tables 45 to 50. The results are shown in Tables 45 to 50. __________________________________________________________________________ t/day 31 32  33 34 35  36 37 38 39  40 41 __________________________________________________________________________ 0 350 350 350 350 350 350 350 350 350 350 350 5 340 340 350 340 350 340 340 340 340 350 350 10 330 340 340 340 340 330 330 330 330 340 340 20 320 330 320 330 320 320 320 320 320 340 340 30 310 320 310 320 310 310 310 310 310 330 330 (Kg/cm.sup.2) __________________________________________________________________________ __________________________________________________________________________ t/day 42 43  44 45 46  47 48 49 50  51 52 __________________________________________________________________________ 0 350 350 350 350 350 350 350 350 350 350 350 5 350 340 350 340 340 340 340 350 350 350 350 10 340 330 340 330 340 340 330 340 340 340 340 20 330 320 330 320 330 340 320 330 330 330 330 30 330 310 330 320 320 330 310 320 320 320 320 (Kg/cm.sup.2) __________________________________________________________________________ __________________________________________________________________________ t/day 53 54  55 56 57  58 59 60 61  62 63 __________________________________________________________________________ 0 350 350 350 350 350 350 350 350 350 350 350 5 340 350 340 350 340 340 340 340 350 350 350 10 330 340 330 340 340 330 330 330 340 340 340 20 320 330 320 330 330 320 330 320 330 330 330 30 310 320 310 320 320 310 310 310 320 320 320 (Kg/cm.sup.2) __________________________________________________________________________ __________________________________________________________________________ t/day 64 65  66 67 68  69 70 71 72  73 74 __________________________________________________________________________ 0 350 350 350 350 350 350 350 350 350 350 350 5 340 340 340 340 340 340 340 340 340 340 340 10 330 340 340 340 330 330 330 340 340 340 340 20 320 330 340 330 330 320 320 330 330 330 330 30 320 320 330 330 310 310 300 310 320 310 320 (Kg/cm.sup.2) __________________________________________________________________________ __________________________________________________________________________ t/day 75 76  77 78 79  80 81 82 83  84 85 __________________________________________________________________________ 0 350 350 350 350 350 350 350 350 350 350 350 5 340 340 350 340 340 340 340 350 350 340 340 10 330 330 340 340 330 330 330 340 340 340 330 20 330 320 330 330 320 330 320 330 330 330 320 30 320 310 320 320 310 310 310 320 320 320 310 (Kg/cm.sup.2) __________________________________________________________________________ ______________________________________ t/day 86      87      88    89    90    91    92 ______________________________________ 0   350     350     350   350   350   350   350 5   340     350     340   340   340   340   350 10   330     340     340   330   330   330   340 20   320     330     330   320   330   320   330 30   310     320     320   310   310   310   320 (Kg/cm.sup.2) ______________________________________

A polyethylene terephthalate PET! resin manufactured by KANEBO LTD. (Product No. EFG-7) and 0.5% by weight of the present hydrolysis stabilizer for an ester group-containing resin comprising as the main component one of the carbodiimides obtained in Synthesis Examples 31 to 92 were melt-mixed and extruded using a twin screw extruder and then formed into a film of about 500 .mu.m using a T-die, after which the film thus obtained was injection molded to obtain JIS-K6301 Dumbbell No. 4. The sample thus obtained was immersed in hot water at 95.degree. C. and the tensile strength was measured by a tensile tester every time shown in Tables 51 to 56. The results are shown in Tables 51 to 56. __________________________________________________________________________ t/day 31 32  33 34 35 36 37 38 39  40 41 __________________________________________________________________________ 0 630 630 630 630 630 630 630 630 630 630 630 10 650 640 650 650 640 650 650 650 640 640 650 30 650 650 640 650 650 650 640 640 640 650 650 60 620 620 640 620 620 630 640 630 630 640 640 (Kg/cm.sup.2) __________________________________________________________________________ __________________________________________________________________________ t/day 42 43  44 45 46 47 48 49 50  51 52 __________________________________________________________________________ 0 630 630 630 630 630 630 630 630 630 630 630 10 650 650 640 650 650 650 650 650 640 650 650 30 640 650 650 650 640 650 650 650 640 640 650 60 630 630 640 640 630 640 630 640 620 610 610 (Kg/cm.sup.2) __________________________________________________________________________ __________________________________________________________________________ t/day 53 54  55 56 57 58 59 60 61  62 63 __________________________________________________________________________ 0 630 630 630 630 630 630 630 630 630 630 630 10 640 640 650 650 650 650 640 650 650 650 650 30 650 640 650 650 650 640 650 650 650 640 640 60 630 620 620 630 620 610 610 620 610 610 610 (Kg/cm.sup.2) __________________________________________________________________________ __________________________________________________________________________ t/day 64 65  66 67 68 69 70 71 72  73 74 __________________________________________________________________________ 0 630 630 630 630 630 630 630 630 630 630 630 10 640 640 640 650 650 640 650 650 650 650 650 30 640 650 650 650 650 640 650 650 650 650 650 60 640 630 640 610 610 600 610 610 630 610 620 (Kg/cm.sup.2) __________________________________________________________________________ __________________________________________________________________________ t/day 75 76  77 78 79 80 81 82 83  84 85 __________________________________________________________________________ 0 630 630 630 630 630 630 630 630 630 630 630 10 650 640 640 650 650 640 650 650 650 640 650 30 640 650 650 650 650 640 650 650 650 640 650 60 610 630 640 610 610 600 610 610 610 600 610 (Kg/cm.sup.2) __________________________________________________________________________ ______________________________________ t/day 86      87      88    89    90    91    92 ______________________________________ 0   630     630     630   630   630   630   630 10   640     650     650   640   650   650   650 30   650     650     650   640   650   650   650 60   640     610     610   600   610   610   610 (Kg/cm.sup.2) ______________________________________

As described above, the present hydrolysis stabilizer for an ester-containing resin has an excellent compatibility with the ester group-containing resin and can be added to the resin without causing any trouble when the resin was synthesized and melt-kneaded. Moreover, since the hydrolysis stabilizer has a high molecular weight, it can sufficiently exhibit the hydrolysis stabilizing effect on the resin.

The present process for the hydrolysis stabilization of an ester group-containing resin comprises mixing the above-mentioned hydrolysis stabilizer with the ester group-containing resin, and hence, can be easily carried out.

## Claims

1. A process for the hydrolysis stabilization of an ester group-containing resin, which comprises mixing the ester group-containing resin with a carbodiimide having at least two carbodiimide groups in the molecule and produced by carboniimidization of 4,4'-dicyclohexylmethane diisocyanate represented by the formula (I): ##STR7## or isophorone diisocyanate represented by the formula (II): ##STR8## or a mixture of 4,4'-dicyclohexylmethane diisocyanate of the formula (I) and isophorone diisocyanate of the formula (II).

2. A process for the hydrolysis stabilization of an ester group-containing resin according to claim 1, wherein the carbodiimide is end-blocked with a primary or secondary amine, a carboxylic acid, an acid anhydride or a monoisocyanate.

3. A process for the hydrolysis stabilization of an ester group-containing resin according to claim 1, wherein the carbodiimide has an average degree of polymerization of 2 to 30.

4. A process for the hydrolysis stabilization of an ester group-containing resin, which comprises mixing the ester group-containing resin with a carbodiimide having at least two carbodiimide groups in the molecule and produced by the carbodiimidization a mixture of tetramethylxylylene diisocyanate represented by the formula (III): ##STR9## with 4,4'-dicyclohexylmethane diisocyanate represented by the formula (I): ##STR10## or isophorone diisocyanate represented by the formula (II): ##STR11## or a mixture of 4,4'-dicyclohexylmethane diisocyanate of the formula (I) and isophorone diisocyanate of the formula (II).

5. A process for the hydrolysis stabilization of an ester group-containing resin according to claim 4, wherein the carbodiimide is end-blocked with a primary or secondary amine, a carboxylic acid, an acid anhydride or a monoisocyanate.

6. A process for the hydrolysis stabilization of an ester group-containing resin according to claim 4, wherein the carbodiimide has an average degree of polymerization of 2 to 30.