JPH0360345B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polypropylene composition suitable for injection molding, which has excellent transparency, rigidity and impact resistance, and suppresses clouding that occurs during storage. Polypropylene resin is used in various molded products due to its excellent rigidity, processability, heat resistance, mechanical properties, etc. However, polypropylene resin has poor transparency due to its high crystallinity and poor impact resistance, making it difficult to use it in applications that require all of transparency, rigidity, and impact resistance. . Therefore, in order to improve transparency, a method was adopted in which propylene was randomly copolymerized with small amounts of α-olefins such as ethylene, butene-1, hexane-1, etc., but these methods had a certain degree of transparency. Although the improvement effect was recognized, it could hardly be called sufficient. In addition, although the impact resistance has been improved to some extent, the decrease in rigidity is significant, and as the degree of improvement in transparency and impact resistance is increased, the amount of by-product of amorphous polymers with poor commercial value increases. There was a problem in which the production of random copolymers suddenly became difficult. In addition, from the perspective of additive formulation, it is known that transparency and rigidity can be simultaneously improved by incorporating dibenzylidene sorbitol or bis(alkylbenzylidene) sorbitol into propylene homopolymer. The impact resistance of the product tended to be lower than that of the propylene homopolymer before blending. Furthermore, propylene-based random copolymers have the disadvantage that when they are left at high temperatures (50 to 60° C. or higher) for long periods of time, they become cloudy, which significantly impairs their commercial value, and it was essential to solve this problem. In view of this situation, the present inventors have conducted extensive research and have found that by blending specific additives into a propylene block copolymer with a specific structure, a product with excellent transparency, rigidity, and impact resistance can be obtained. The present inventors have also discovered that a polypropylene resin composition can be obtained in which cloudiness that occurs during storage is suppressed, leading to the present invention. That is, the present invention provides a propylene homopolymer block with a melt flow rate (MFR) reduced from 0.05 to 10 g/10 minutes to 10 to 100 g/10 minutes in the presence of a radical generator and an ethylene content of 5 to 95% by weight. It is characterized by consisting of 100 parts by weight of a propylene block copolymer consisting of 95 to 5% by weight of a propylene/ethylene random copolymer block of 2 to 15% by weight, and 0.05 to 0.5 parts by weight of a compound of the following formula [] It is a polypropylene composition. (R is an alkyl group having 1 to 5 carbon atoms, an alkoxy group, a halogen atom, or a hydroxyl group; m and n are 0 to 3
an integer; R may be different in the same compound, and m and n may be the same in the same compound. ) The propylene-based block copolymer used in the present invention has a propylene homopolymer block content of 5 to 95% by weight (preferably 10 to 90% by weight, more preferably 15% by weight).
~85% by weight) and ethylene content 2-15% by weight
(preferably 2.5 to 13% by weight, more preferably 3 to 13% by weight)
10% by weight) propylene/ethylene random copolymer block (preferably 90 to 10% by weight, more preferably 85 to 15% by weight), and has an MFR of 0.05 to 10g before degradation. /10 minutes is suitable. The proportion of the propylene homopolymer block and the propylene/ethylene random copolymer block can be selected from a wide range depending on the desired balance of physical properties; If the proportion of the combined block is high and the physical property balance with emphasis on impact resistance is desired, the proportion of the propylene/ethylene random copolymer block can be set high. Any deviation from the above ratio range will disrupt the balance between rigidity and impact resistance. Propylene homopolymer block and propylene
When the proportion of the ethylene random copolymer blocks is kept constant, by increasing the ethylene content in the random copolymer blocks, the impact resistance can be significantly improved with almost no decrease in the rigidity of the block copolymer. is possible. However, it was found that the transparency decreased at the same time. However, as long as the ethylene content is within the above range, as will be described later, by incorporating specific additives, It is possible to significantly improve transparency and haze during storage without significantly reducing the increased impact resistance. Furthermore, advantageously, if the ethylene content exceeds the above range, which also slightly improves the stiffness, the transparency not only deteriorates to an extent that cannot be recovered even with specific additive formulations, but also blocks co-existence. The amount of amorphous polymer produced as a by-product during polymer production increases rapidly, deteriorating productivity. Such block copolymers are generally produced by directly applying the production techniques for propylene homopolymers or random or block copolymers of propylene and ethylene. That is, it is produced by a multistage polymerization method including polymerization steps including a propylene homopolymerization step and a propylene/ethylene random polymerization step using a Ziegler type stereospecific polymerization catalyst in the presence or absence of an inert solvent. Molecular weight is controlled by hydrogen. As the Ziegler type stereospecific polymerization catalyst, a catalyst system containing various titanium trichloride or magnesium chloride-supported titanium-containing catalysts and an organoaluminum compound such as diethylaluminum chloride or triethylaluminum as the main components can be suitably used. The composition containing the block copolymer of the present invention is different from the composition obtained by using a mechanical blend of a propylene homopolymer and a propylene/ethylene random copolymer instead of the block copolymer. It has the following advantages in terms of physical properties and economy. Generally, when a propylene/ethylene random copolymer is produced using a Ziegler-type stereospecific catalyst, an amorphous rubber-like copolymer is produced as a by-product at the same time as copolymer particles that retain crystallinity. The amount of copolymer by-products tends to increase rapidly as the ethylene content in the copolymer increases. Therefore, due to process stability and economic constraints, the ethylene content in the copolymer has to be controlled by engineering. The upper limit is considered to be about 5% by weight. However, when a propylene homopolymer block is produced and then a propylene/ethylene random copolymer block is produced by a two-stage polymerization method, surprisingly, the ethylene content in the random copolymer block is reduced to 15%. It was found that the amount of rubbery copolymer by-product was within an acceptable range even if the amount was increased to about % by weight. This means that a polymer structure that cannot be realized industrially using the blending method can be realized for the first time using the block copolymerization method.How does this contribute to improving the physical property balance of the final composition? can be easily understood from the explanations given so far. If the MFR of the propylene block copolymer obtained in this way is less than 0.05 g/10 minutes, not only will clouding occur significantly during storage, but
It is not desirable because controlling MFR itself is difficult.
On the other hand, if it exceeds 10 g/10 minutes, there is little room for deterioration in subsequent steps, which not only reduces the effect of improving impact resistance due to confinement, but also causes clouding to occur again during storage, which is not preferable. By the way, the block copolymer (MFR: 0.05 to 10 g/10 min) obtained by the copolymerization reaction itself has
When the specific additives mentioned below are added, it exhibits some degree of excellent transparency, rigidity, and impact resistance, but this block copolymer is degraded in the presence of a radical generator to achieve an MFR of 10 to 100. When made into injection molded products, especially thin-walled injection molded products, the impact resistance, especially the surface impact strength, and the suppression of clouding during storage are further improved compared to those set to the equivalent MFR through copolymerization alone. do. Normally, molecular weight reduction by radical generators is
It is carried out by pelletizing the copolymer in an extruder at a temperature of 180 to 300°C in the presence of a radical generator such as peroxide. Preferred radical generators include organic peroxides such as hydroperoxides, alkyl peroxides, acyl peroxides, ketone peroxides, alkyl peresters, peroxydicarbonates, and silicone peroxides. and azo compounds are preferred, specifically t-butyl hydroperoxide,
Dicumyl peroxide, 1,3-bis(t-butylperoxyisopropyl)benzene, benzoyl peroxide, methyl isobutyl ketone peroxide, t-butyl perbenzoate, diisopropyl peroxydicarbonate, vinyl tris(t-butylperoxy) Silane, azobisisobutylnitrile, 2,2-azobis(2,
4-dimethylvaleronitrile) and the like.
The amount of these radical generators used is generally in the range of 0.001 to 0.5 parts by weight based on 100 parts by weight of the copolymer. When kneading for degradation, antioxidants, lubricants, mold corrosion inhibitors, ultraviolet absorbers, etc. may be added at the same time. If the MFR of the degraded propylene block copolymer thus obtained is less than 10 g/10 minutes, injection moldability will be insufficient, and the degradation width will become small, resulting in poor resistance as a degradation effect. This is not preferable because the effect of improving impact resistance becomes poor; on the other hand, 100g/
If the time exceeds 10 minutes, the impact resistance especially after application of the material decreases, which is not preferable. Furthermore, dibenzylidene sorbitol or bis(substituted benzylidene) sorbitol used in the present invention has the general formula (R is an alkyl group having 1 to 5 carbon atoms, an alkoxy group, a halogen atom, or a hydroxyl group; m and n are 0 to 3
an integer; R may be different in the same compound, and m and n may be the same in the same compound. ) is a compound represented by Specifically, for example,
Dibenzylidene sorbitol, 1,3,2,4-
di(p-methylbenzylidene) sorbitol,
1,3,2,4,-di(p-chlorobenzylidene)
Examples include sorbitol, 1,3,2,4-di(p-methoxybenzylidene) sorbitol, and the like. This compound is blended in an amount of 0.05 to 0.5 parts by weight, preferably 0.1 to 0.3 parts by weight, per 100 parts by weight of the propylene block copolymer. If it is less than 0.05 parts by weight, there will be almost no improvement in transparency or clouding control, and if it exceeds 0.5 parts by weight, problems such as bleeding may occur.
Economic efficiency is also not favorable. The most rational way to add this substance is to utilize the degradation process using the radical generator described above. In addition, various additives can be appropriately blended into the composition of the present invention within a range that does not impair the effects of the invention. Specifically, antioxidants, light stabilizers,
Examples include ultraviolet absorbers, nucleating agents, antistatic agents, pigments, pigment dispersants, lubricants, neutralizing agents, and acid scavengers. In particular, it is preferable to add antioxidants to maintain the stability of granulation and molding processes, and neutralizing or hydrochloric acid scavengers such as metal soaps and hydrotalcites exhibit the effects of this patent. This is more preferable. Example 1 After sufficiently replacing the inside of a stainless steel reactor with an internal volume of 200 mm equipped with a stirring blade with propylene gas,
Heptane 80 was added as a polymerization solvent. The temperature inside the vessel was maintained at 50° C., and 50 g of diethyl aluminum chloride (DEAC) and 10 g of titanium trichloride (TMB-07, manufactured by Marubeni Solvay Chemical Co., Ltd.) were added as catalysts. Propylene was then fed at a rate of 5.83 Kg/hr for 15 minutes. During this time, the concentration of hydrogen in the gas phase was 2.0.
% by volume. Next, increase the temperature inside the vessel to 60℃.
The hydrogen concentration was increased to 6.8% by volume, and propylene was continuously fed at a rate of 5.83 kg/hour for 75 minutes. The total amount of propylene supplied during this period was 7.3Kg. (The above is a propylene homopolymer block). Ethylene was newly fed at a rate of 0.276 kg/hour while maintaining the internal temperature, hydrogen concentration, and propylene feed rate, and propylene and ethylene were each fed for 285 minutes. During this period, the total supply of propylene and ethylene was 27.7Kg and
It weighed 1.31Kg. At this point, the internal pressure was 4.1Kg/
cm ² (gauge pressure), but at this point the supply of propylene and hydrogen stopped, and the ethylene
While feeding at a rate of 0.193 Kg/hour, the pressure inside the vessel was lowered to 2.0 Kg/cm ² (gauge pressure) over 40 minutes to complete the reaction. The total supply of ethylene during this period was 0.129
It was Kg. (The above is a propylene/ethylene random copolymer block). Butanol 1.1 to the obtained block copolymer
After the catalyst was decomposed at 68° C. for 3 hours, the catalyst was removed by washing with water. After further centrifugation and drying steps, 32.5 kg of product copolymer was obtained. In addition, the amorphous copolymer produced as a by-product after being dissolved in the polymerization solvent is
It weighed 1.30Kg. The proportion of the propylene homopolymer block and the propylene-ethylene random copolymer block in the block copolymer is calculated by subtracting the amount of unreacted monomer and the amount of by-product amorphous polymer from the total amount of monomer supplied. It was calculated by allocating it to the ratio of the amount of monomers supplied to produce the polymer block. The ethylene content of the propylene/ethylene random copolymer block portion was calculated from the ratio of both blocks calculated above and the ethylene content in the product block copolymer. To 100 parts by weight of the block copolymer thus obtained, tetrakis[methylene (3,5-di-t-
-butyl-4-hydroxydrocinnamate)]
Butane (antioxidant) 0.1 part by weight, calcium stearate (neutralizing agent) 0.1 part by weight, 1, 3, 2,
4-di(paramethylbenzylidene)sorbitol
0.2 parts by weight and 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (peroxide)
0.025 parts by weight was added, mixed, and granulated at 250°C. The block copolymer composition pellets were put into an injection molding machine with a screw diameter of 40 mm (cylinder set temperature
(240°C) to prepare specimens. Three-point bending modulus (based on JIS-K7203) and Izod impact value (based on JIS-K7110) were measured for this specimen.
Haze (according to JIS-K6714) and Dupont impact strength were measured on specimens measuring 100 x 100 x 1 mm thick. The degree of cloudiness was evaluated by measuring the haze after holding a test piece for haze measurement in an oven at 60° C. for 48 hours and comparing it with the haze before oven treatment. Generally, the haze difference needs to be within 3%. MFR was measured in accordance with JIS-K7210. The results are shown in Table 1. Examples 2 to 4 1,3,2,4-dibenzylidene sorbitol, 1,3,2,4-di(parachlorobenzylidene) sorbitol instead of 1,3,2,4-di(paramethylbenzylidene) sorbitol A block copolymer was produced and a sheet was formed in the same manner as in Example 1, except that 1,3,2,4-di(paramethoxybenzylidene)sorbitol was used. The results are shown in Table 1. Example 5 After the temperature inside the polymerization vessel reached 60°C, the propylene supply time during the propylene homopolymer block production stage was 185 minutes (therefore, the total amount of propylene supplied was 18.0 kg), and the gas phase portion during this period was The hydrogen concentration was set to 6.0% by volume, the ethylene supply rate at the propylene-ethylene random copolymer block production stage was 0.333Kg/hour, and the supply time during simultaneous supply of propylene and ethylene was 175 minutes (therefore, during this period 17.0Kg and 0.97Kg, respectively), and the ethylene supply rate and time after stopping the propylene supply are 0.233Kg/hour and 30 minutes, respectively (so the total supply of ethylene during this period is 0.117Kg/hour and 30 minutes, respectively). A block copolymer was produced in the same manner as in Example 1, except that the copolymer was prepared in a manner similar to that of Example 1. Further, the obtained block copolymer was formed into a sheet under the same conditions as in Example 1, and its physical properties were measured. The results are shown in Table 1. Example 6 The propylene supply time in the propylene homopolymer block production stage after the temperature inside the polymerization vessel reached 60°C was 250 minutes (therefore, the total amount of propylene supplied was 18.0 kg), and the gas phase during this period was The hydrogen concentration in the block was set at 6.5% by volume, the ethylene supply rate at the propylene-ethylene random copolymer block manufacturing stage was set at 0.530 kg/hour, and the supply time during simultaneous supply of propylene and ethylene was set at 110 minutes (therefore, , the total supply of propylene and ethylene during this period was 10.7Kg and 0.97Kg, respectively), and the ethylene supply rate and time after stopping the propylene supply were 0.675Kg/hour and 22 minutes, respectively (therefore, the total supply of ethylene during this period was 0.675Kg/hour and 22 minutes, respectively). A block copolymer was produced in the same manner as in Example 1, except that the amount was changed to 0.248 kg). Further, the obtained block copolymer was molded into a sheet under the same conditions as in Example 1, and its physical properties were measured. The results are shown in Table 1. Comparative Examples 1 to 3 The block copolymers of Examples 1, 5, and 6 were used, except that the additive 1,3,2,4-di(paramethylbenzylidene) sorbitol was added. Sheets were formed in the same manner as in Examples 5 and 6, and their physical properties were evaluated. Results first
Shown in the table. Comparative Examples 4 to 6 Same polymer structure as Examples 1, 5, and 6 (ratio of propylene homopolymer block to propylene/ethylene random copolymer block and ethylene content in the latter), only MFR was due to peroxide. In order to obtain a block copolymer equal to the value after treatment only by copolymerization reaction, the hydrogen concentration was adjusted to 14.0 and 14.0, respectively, when the temperature inside the polymerization vessel reached 60°C.
Block copolymers were produced under the same conditions as in Examples 1, 5 and 6, except that the amounts were set at 13.2 and 12.8% by volume. The obtained copolymers were formed into sheets in the same manner as in Examples 1, 5, and 6, except that 2,5-dimethyl-2,5-di(t-butylperoxy)hexane was not added, and the physical properties were determined. was evaluated. The results are shown in Table 1. Comparative Examples 7 to 9 Using the same block copolymer as Comparative Examples 4 to 6,
1,3,2,4-di(paramethylbenzylidene)
Comparative Example 4 except that sorbitol was not added.
A sheet was formed under the same conditions as in 6 to 6, and its physical properties were evaluated. The results are shown in Table 1. Comparative Example 10 When the temperature inside the polymerization vessel reached 60°C, the propylene and ethylene random copolymerization step was immediately proceeded without further homopolymerization of propylene, and the propylene and ethylene were simultaneously copolymerized in the random copolymerization step. The supply time was set to 360 minutes, and the hydrogen concentration during this period was changed to 6.7% by volume, and the ethylene supply rate was changed to 0.186Kg/hour (therefore, the total supply amount of propylene and ethylene during this period was changed to 6.7% by volume, respectively).
35.0Kg and 1.12Kg), and the ethylene supply rate after stopping the propylene supply,
Supply time and total supply amount are respectively 0.130Kg/hour, 36
Example 1 except for the minute and 0.078Kg
A block copolymer was produced in the same manner as above. The results are shown in Table 1. Further, this block copolymer was molded into a sheet in the same manner as in Example 1, and its physical properties were evaluated. The results are shown in Table 1. Comparative Example 11 The ethylene supply rate in the random copolymerization stage was 0.350 Kg/hour during the simultaneous supply of propylene and ethylene, and 0.245 Kg/hour after the propylene supply was stopped; The time period during which propylene and ethylene were simultaneously supplied was the same as in Comparative Example 10 (therefore, the total amount of ethylene supplied during this period was 2.10 kg),
The period after the propylene supply was stopped was 28 minutes. (Therefore, the total supply of ethylene during this period is
A block copolymer was produced in the same manner as in Comparative Example 10, except that the weight was 0.114 kg). Further, using this block copolymer, Example 1
A sheet was formed in the same manner as above, and its physical properties were evaluated. The results are shown in Table 1. Comparative Examples 12, 13 Using the propylene/ethylene random copolymer of Example 1, para-t-butylbenzoic acid was added instead of the clarifying agent 1,3,2,4-di(paramethylbenzylidene)sorbitol. Samples were prepared and evaluated in the same manner as in Example 1, except that aluminum (Comparative Example 12) and talc (Comparative Example 13) were added. The results are shown in Table 1.

【table】

【table】

[Table] In Table 1, bis(substituted benzylidene)
The sorbitol type symbols represent the following: A: 1,3,2,4-dibenzylidene sorbitol B: 1,3,2,4-di(p-methylbenzylidene) sorbitol C: 1,3,2,4-di(p-chlorobenzylidene) sorbitol D : 1,3,2,4-di(p-methoxybenzylidene) sorbitol E: pt-butylbenzoic acid aluminum F: Talc (High Filler P-7 manufactured by Matsumura Sangyo Co., Ltd.)

Claims (1)

[Scope of Claims] 1. A homopolymer block of propylene with a melt flow rate reduced from 0.05 to 10 g/10 minutes to 10 to 100 g/10 minutes in the presence of a radical generator and an ethylene content of 2 to 95% by weight. Propylene block copolymer 100 consisting of 95 to 5% by weight propylene/ethylene random copolymer block 15% by weight
Parts by weight, and 0.05 to 0.5 of the compound of the following formula []
A polypropylene composition comprising parts by weight. (R is an alkyl group having 1 to 5 carbon atoms, an alkoxy group, a halogen atom, or a hydroxyl group; m and n are 0 to 3
an integer; R may be different in the same compound,
m and n may be the same in the same compound. )