KR101909577B1 - Manufacturing method of polypropylene composition for higher transparency, softness and shrinkage - Google Patents

Abstract

In a polypropylene resin composition for a shrinkable film containing a propylene-ethylene-1-butene random copolymer, problems of dispersibility in the mixing of an elastomer are solved in order to improve the workability of the prior art, A method for producing a polypropylene resin composition which improves the heat bonding strength without lowering the transparency and the shrinkage rate. (A) 85 to 97% by weight of a crystalline propylene-ethylene-1-butene random copolymer prepared from propylene, ethylene and 1-butene as raw materials and introduced into a mixer in a polymerization reactor; (b) 2 to 10% by weight of an elastomer containing 30 to 95 mol% of 1-butene, which is prepared in the same polymerization reactor as the raw material of (a) and is introduced into the mixer; (c) 1 to 5% by weight of a mixed resin of low density polyethylene and linear low density polyethylene; (d) 0.01 to 0.5 parts by weight of a slip agent based on 100 parts by weight of the total of the components (a) to (c); And (e) 0.01 to 0.5 parts by weight of an anti-blocking agent per 100 parts by weight of the total of the components (a) to (c) in a mixer and extruding the mixture with an extruder to produce a polypropylene resin composition.

Description

TECHNICAL FIELD [0001] The present invention relates to a polypropylene resin composition which is excellent in transparency, softness and shrinkage ratio. BACKGROUND ART [0002]

The present invention relates to a method for producing a polypropylene resin composition, and more particularly to a polypropylene resin composition having excellent transparency, softness and shrinkage.

The shrink film enables packaging in a state of maintaining the shape of the final product, and is generally used for necessities such as cup noodles, stationery, and the like. Such a method for molding a shrinkable film can be generally obtained by biaxial stretching in the transverse direction or longitudinal direction of the film by a double bubble type inflation method.

As the resin for biaxially stretched shrink film, polypropylene, polyvinyl chloride and the like are available. However, when polypropylene is used, it has an advantage of obtaining high transparency and excellent mechanical properties.

Such a polypropylene shrink film resin has conventionally used propylene-ethylene-1-butene random copolymer resin. When this raw material is used alone, biaxial stretchability such as bubble stability, bubble burst, And excellent in transparency and mechanical properties. However, due to the structural problems caused by the crystalline portions of the resin, the resin is limited in its softness, which is limited to small-sized packages, has a limitation in large-sized shrinkable packaging, and has a limitation in high- .

In order to solve this problem, a method of adding an elastomeric product to an extruder in the production process has been proposed, but a problem of poor product uniformity due to a problem of dispersion failure has been raised.

Korean Patent Registration No. 0783554 discloses a polypropylene resin for a biaxially stretched shrink film prepared by adding an amorphous propylene-1-butene copolymer to a polypropylene random copolymer using a propylene-ethylene-1-butene terpolymer There are problems such as non-uniformity of shrinkage due to poor dispersion of the elastomer product added to the extruder and unevenness of transparency of the surface.

Korean Patent Publication No. 0745323 discloses a polypropylene resin composition for a shrink film having improved shrinkability and transparency by including a propylene-1-butene copolymer in a crystalline ethylene-propylene-1-butene terpolymer, There is a limitation in the shrink packaging of the large-sized product due to the low quality, and there is a limit to the high-speed packaging due to the low-temperature heat sealing composition.

U.S. Patent No. 5,888,640 discloses a polypropylene resin using a propylene-ethylene copolymer or a propylene-ethylene-1-butene terpolymer in which a syndiotactic polypropylene resin using metallocene is used to improve shrinkage properties Although the polypropylene resin composition has a somewhat low shrinkage rate, the syndiotactic polypropylene resin has a high melting temperature and has a limitation in improving the shrinkage percentage.

On the other hand, the applicant of the present invention has disclosed in Patent Application No. 2014-0160727 that the same raw material as the propylene-ethylene-1-butene random copolymer is prepared in the same polymerization reactor and mixed with the elastomer fed into the mixer and extruded, A method of producing a resin composition has been proposed. However, since the elastomer content is high, there is a problem that the heat bonding strength is lowered when an actual product is applied.

Disclosure of the Invention The present invention has been conceived to solve the above problems, and it is an object of the present invention to solve the problem of dispersibility in the mixing of an elastomer in order to improve the processability in a polypropylene resin composition for a shrinkable film containing a propylene- To provide a method for producing a polypropylene resin composition which is suitable for shrink packaging and high-speed packaging of a large-sized article, and which improves the heat bonding strength without lowering transparency and shrinkage.

In order to solve the above problems, the present invention provides a method for producing a polypropylene resin composition by extruding the following components in a mixer and an extruder.

(a) 85 to 97% by weight of a crystalline propylene-ethylene-1-butene random copolymer prepared from propylene, ethylene and 1-butene as raw materials in a polymerization reactor and introduced into a mixer;

(b) 2 to 10% by weight of an elastomer containing 30 to 95 mol% of 1-butene, which is prepared in the same polymerization reactor as the raw material of (a) and is introduced into the mixer;

(c) 1 to 5% by weight of a mixed resin of low density polyethylene and linear low density polyethylene;

(d) 0.01 to 0.5 parts by weight of a slip agent based on 100 parts by weight of the total of the components (a) to (c); And

(e) 0.01 to 0.5 parts by weight of an anti-blocking agent per 100 parts by weight of the components (a) to (c).

The crystalline propylene-ethylene-1-butene random copolymer contains 1 to 10 mol% of ethylene and 1 to 10 mol% of 1-butene in the propylene component, and has a melt index (230 DEG C, 2.16 kg load) / 10 min, and the melting temperature is 135 DEG C or lower.

The elastomer is a non-crystalline amorphous polypropylene resin which contains 1 to 30 mol% of ethylene and 40 to 70 mol% of 1-butene in a propylene component and has a melt index (230 DEG C, 2.16 kg load) of 1 to 10 g / Wherein the composition is a composition.

The mixed resin (c) contains 20 to 30% by weight of the low-density polyethylene and 70 to 80% by weight of the linear low-density polyethylene and has a melt index (190 DEG C, 2.16 kg load) of 10 to 15 g / 0.920 to 0.925 g / cm < 3 >.

The slip agent may also be selected from the group consisting of erucamide, oleamide, behenamide stearamide, stearyl stearamidel, stearyl erucamide, And at least one amide-based slipping agent selected from the group consisting of oleyl palmitate amide.

And the anti-blocking agent is silica or zeolite.

According to the method for producing a polypropylene resin composition of the present invention, the elastomer component to be mixed and extruded into the propylene-ethylene-1-butene random copolymer is used as the same component as the propylene-ethylene-1-butene random copolymer, Is used for the shrink film for high-volume packaging and high-speed packaging which are difficult to apply to existing products by giving high shrinkability, transparency and low-temperature heat-sealing synthesis by using the elastomer produced in It is possible to provide a method for producing a polypropylene resin composition which can dramatically improve the heat bonding strength without decreasing the transparency and the shrinkage while using a relatively small amount of the elastomer through controlling the 1-butene content among the elastomer components have.

Hereinafter, the present invention will be described in detail with reference to preferred embodiments. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately The present invention should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention. Accordingly, it is to be understood that the constituent features of the embodiments described herein are merely the most preferred embodiments of the present invention, and are not intended to represent all of the inventive concepts of the present invention, so that various equivalents, And the like.

(A) 85 to 97% by weight of a crystalline propylene-ethylene-1-butene random copolymer prepared from propylene, ethylene and 1-butene as raw materials and introduced into a mixer in a polymerization reactor; (b) 2 to 10% by weight of an elastomer containing 30 to 95 mol% of 1-butene, which is prepared in the same polymerization reactor as the raw material of (a) and is introduced into the mixer; (c) 1 to 5% by weight of a mixed resin of low density polyethylene and linear low density polyethylene; (d) 0.01 to 0.5 parts by weight of a slip agent based on 100 parts by weight of the total of the components (a) to (c); And (e) 0.01 to 0.5 parts by weight of an anti-blocking agent per 100 parts by weight of the total of the components (a) to (c) are mixed and extruded in a mixer to produce a polypropylene resin composition. Hereinafter, each component constituting the present invention will be described in detail.

(a) a crystalline propylene-ethylene-1-butene random copolymer

In the present invention, the crystalline propylene-ethylene-1-butene random copolymer is prepared in a polymerization reactor using propylene, ethylene and 1-butene as raw materials, and is introduced into a mixer and mixed with other components to be described later and supplied to the extruder.

The crystalline propylene-ethylene-1-butene random copolymer may contain 1 to 10 mol% of ethylene and 1-butene, respectively, and the remaining 80 to 98 mol% of propylene. The melting temperature by DSC is preferably 135 占 폚 or lower, and the melt index is preferably 3 to 10 g / 10 min (230 占 폚, 2.16 kg).

This propylene-ethylene-1-butene random copolymer can maintain bubble stability, bubble burst, film thickness variation, and the like during biaxial stretching due to inflation while maintaining the transparency of the polypropylene resin composition of the present invention, ≪ / RTI > component with good optical and thermodynamic compatibility.

When the content of ethylene and 1-butene constituting the propylene-ethylene-1-butene random copolymer is less than 1 mol%, the degree of crystallization of the copolymer becomes higher than necessary, thereby increasing the heat sealing temperature of the resultant composition and increasing the softness If it is more than 10 mol%, the crystallinity is rapidly lowered and the adhesion due to low molecular weight is increased, which may cause blocking of the film.

If the melt index of the propylene-ethylene-1-butene random copolymer is less than 3 g / 10 min, the extrusion amount may be lowered, and if it exceeds 10 g / 10 min, the bubble may be shaken. If the melting temperature is higher than 135 ° C, the degree of crystallization of the copolymer becomes higher than necessary, thereby increasing the heat sealing temperature of the resulting composition and improving the softness.

In the present invention, the content of the crystalline propylene-ethylene-1-butene random copolymer is 85 to 97% by weight in the total resin composition in consideration of the elastomer content to be described later.

(b) Propylene-ethylene-1-butene elastomer

In the present invention, the elastomer is an elastomer for maximizing the heat bonding strength without decreasing the transparency and the shrinkage rate while reducing the content of the entire polypropylene resin composition as compared with the conventional one. The elastomer is composed of the same raw material as the raw material (a) Butene based elastomer, i.e., an elastomer having a relatively high 1-butene content.

Therefore, in the present invention, the elastomer is an elastomer produced in the same polymerization reactor as the raw material (a) and charged into the mixer, wherein the elastomer containing 30 to 95 mol% of 1-butene is contained in the total polypropylene resin composition, 10% by weight.

The propylene-ethylene-1-butene elastomer is an elastomer having the same composition as the crystalline propylene-ethylene-1-butene random copolymer (a) Propylene, ethylene and 1-butene, which are used in the same polymerization reactor, are fed into a mixer and mixed with other components and supplied to the extruder.

That is, in the conventional extrusion process using a crystalline propylene-ethylene-1-butene random copolymer, an elastomer product which is separately prepared with a composition different from that of the crystalline propylene-ethylene-1-butene random copolymer component is mixed with the extruder However, in the present invention, an elastomer is prepared and mixed with the propylene, ethylene, and 1-butene raw materials fed in the same line by using the same reactor and by adjusting the content thereof, reaction conditions, -Butene random copolymer, thereby giving a high shrinkage ratio, transparency and low-temperature heat sealing composition.

The propylene-ethylene-1-butene elastomer is an amorphous polypropylene resin composition having no crystallinity and has a melting temperature of 100 DEG C or lower and a softening point temperature of 80 DEG C or lower, preferably 1 to 30 mol% 40 to 70 mol% of butene, and a melt index (230 DEG C, 2.16 kg load) of 1 to 10 g / 10 min.

When the content of 1-butene is less than 40 mol%, the elastomer tends to have poor softness, and the heat bonding strength may be lowered. When the content is more than 70 mol%, the transparency may be deteriorated. If the melt index is less than 1 g / 10 min, the extrusion amount may be lowered. If the melt index exceeds 10 g / 10 min, the bubble may be shaken. If the melting temperature is higher than 100 ° C, the degree of crystallization of the copolymer becomes higher than necessary, thereby increasing the heat sealing temperature of the resulting composition and increasing the softness. Further, even when the softening point temperature exceeds 80 ° C, a problem of increasing the heat sealing temperature and softness may occur.

On the other hand, the propylene-ethylene-1-butene elastomer is preferably produced using a metallocene catalyst, and has a molecular weight distribution narrower than that copolymerized with a Ziegler-Natta catalyst, so that blocking due to adhesion of a low molecular weight polymer is small , Has a low melting temperature, is excellent in the synthesis of a low temperature heat seal, and can have softness with a low surface hardness.

In the present invention, the propylene-ethylene-1-butene elastomer is contained in an amount of 2 to 10 wt% of the resin component of the final composition. When the content of propylene-ethylene-1-butene elastomer is less than 2% by weight, transparency is good, but softness and heat bonding strength may be deteriorated. When it exceeds 10% by weight, , The biaxial stretching processability such as film thickness deviation is lowered, and the heat bonding strength may be lowered.

(c) Mixed resin of low density polyethylene and linear low density polyethylene

In the present invention, the mixed propylene-ethylene-1-butene random copolymer and the propylene-ethylene-1-butene elastomer as the resin component together with the crystalline propylene-ethylene-1-butene random copolymer and the low-density polyethylene and the linear low density polyethylene are used to further improve the bubble stability.

In order to improve the bubble stability, the mixed resin includes 20 to 30% by weight of the low-density polyethylene and 70 to 80% by weight of the linear low-density polyethylene and has a melt index (190 ° C, 2.16 kg load) of 10 to 15 g / It is preferable to use one having a density of 0.920 to 0.925 g / cm3.

(d) Slip agent

In the present invention, the slip agent is added to the film surface to reduce the sticky phenomenon and improve the slip of the surface, and it is preferable to use an amidic slip agent. That is, the amide slip agent can be preferably used as a compound having a high melting point of amide series synthesized from a fatty acid and having a hydroxyl group substituted with an amino structure to have a neutral structure.

Examples of the amide-based slipping agent include, but are not limited to, erucamide, oleamide, behenamide stearamide, stearyl stearamidel,

Stearyl erucamide, oleyl palmityl amide, and the like.

The slip agent preferably has an average particle diameter of 1 to 2 mm, preferably 1.1 to 1.5 mm, and an average particle diameter of 0.1 to 0.9 mm, preferably 0.2 to 0.6 mm.

Such a slip agent is a resin composition comprising 100 parts by weight of a mixed resin of a crystalline propylene-ethylene-1-butene random copolymer, propylene-ethylene-1-butene elastomer, low density polyethylene and linear low density polyethylene By weight based on the total weight of the composition. If the content of the slip agent is less than 0.01 parts by weight, the film may be deteriorated. If the amount of the slip agent is more than 0.5 parts by weight, the slip property may be excessively increased.

(e) Anti-blocking agent

In the present invention, the anti-blocking agent is added to minimize the migration of the soluble fraction because the anti-blocking agent serves to trap the low molecular weight material on the surface of the film, so that silica or zeolite can be used.

Wherein the silica is a conventional silica of the silica, but may be used, porous white amorphous known in the art and is not particularly limited, a particle size of 2 ~ 5.3㎛, the volume of the pores is 0.4 ~ 0.8㎖ / g, SiO ₂ Is preferably 99 mol% or more. It is also preferable to use particles having a water content of less than 2% by weight when dried at 160 캜.

The zeolite is not particularly limited, and conventional zeolites known in the art can be used. For example, monoclinic zeolite can be used. The size of the zeolite particles should be within a range that does not lower the degree of fogging of the film, so that the size of zeolite particles synthesized using sodalite is preferably 2 to 5 μm. Also, the bulk density of the particles is 0.3 to 0.5 g / ml, the average pore interconnected channel is 5 to 15 angstroms, preferably 7 to 12 angstroms, and the specific surface area is 80 to 200 mils / g, a pH of 8 to 9, and a whiteness of 95 or more.

Such an anti-blocking agent is a resin composition comprising 100 parts by weight of a mixed resin of a crystalline propylene-ethylene-1-butene random copolymer, propylene-ethylene-1-butene elastomer, low density polyethylene and linear low density polyethylene 0.01 to 0.5 parts by weight based on 100 parts by weight of the composition. When the content of the anti-blocking agent is less than 0.01 part by weight, the printing property and blocking property of the product using the polypropylene resin composition may be deteriorated. If the content is more than 0.5 part by weight, the transparency of the product may be deteriorated.

In preparing the polypropylene resin composition of the present invention, one or more conventional additives known in the art may be further added as other additives in addition to the above components, for example, an antioxidant, a neutralizing agent, an ultraviolet stabilizer, and an antistatic agent. In this case, each of the additives may be included in the range of 0.01 to 1 part by weight based on 100 parts by weight of the resin composition of the present invention.

The antioxidant is used for preventing the resin molecules from being broken by heat, oxygen, or the like when the film is produced by using the polypropylene resin composition. The neutralizing agent is generated by the residue (metal component) of the catalyst used in the polymerization To neutralize the acid (e.g., HCl) that may be present. Further, the ultraviolet stabilizer is for preventing the molecular chains of the resin from being broken by ultraviolet rays, and the antistatic agent is for reducing the generation of static electricity in a film produced by using the polypropylene resin composition.

In the present invention, the mixing and extrusion of the components may be performed according to a conventional method known in the art. For example, the crystalline propylene-ethylene-1-butene random copolymer and propylene-ethylene-1-butene elastomer prepared in the same polymerization reactor and other components are added to the Henschel mixer in the required amount, and the Henschel mixer is heated at 300 to 700 rpm The mixture was mixed for 0.1 to 2 minutes under the condition of 0.5 to 3 minutes and 1,200 to 1,800 rpm under the condition of 300 to 700 rpm for a total of 2 to 8 minutes. To 230 deg. C, preferably 180 deg. 220 deg. C, and a L / D of 25 or greater, a multi-screw extruder, a kneader or a Benbury mixer. Preferably, the polypropylene resin composition can be prepared using a 40 mm co-axial direction twin-screw extruder having an L / D ratio of 40 and a side feeder under the processing conditions of an extruder having a forming temperature of 160 to 220 ° C and an extruder having a forming speed of 300 to 500 rpm have.

The polypropylene resin composition of the present invention can be molded into a molded article using a known molding method, and can be preferably formed into a film, more preferably a film for low temperature thermal bonding. For example, a film can be prepared from a polypropylene resin composition through a process of stretching a film that has been cooled with water through a circular die at a high temperature of 100 to 150 ° C by using an extruder having a molding temperature of 150 to 220 ° C.

Hereinafter, the present invention will be described in detail with reference to examples.

Example  One

(a) A crystalline propylene-ethylene-1-butene random copolymer (ethylene content: 5 mol%, 1-butene content: 3.5 mol%, melt index Propylene-ethylene-1-butene elastomer (ethylene content: 10 mol%, 1-butene content: 50 mol%, produced by using the polymerization reactor and the same raw materials) (A melt index (190 占 폚, 2.16 kg load (weight)) of 2% by weight of a low density polyethylene and 25% by weight of a low density polyethylene and 75% by weight of a linear low density polyethylene (D) 0.5 parts by weight of an amide-based slipping agent based on 100 parts by weight of the total of the components (a) to (c) and (e) c) 0.5 parts by weight of the porous silica blocking agent was added to 100 parts by weight of the total of components, and the Henschel mixer was operated under conditions of 500 rpm for 1 minute and 1,500 rpm For 0.5 minutes and then mixed again at 500 rpm to discharge the sample out. The mixture was thoroughly mixed for 3 to 5 minutes, and then the working temperature was adjusted to 180 to 220 ° C using a 40 mm single screw extruder having an L / D of 35 Thereby preparing a polypropylene resin composition. Thereafter, a film was prepared from the polypropylene resin composition by a process of stretching the resin composition, which had been cooled with water through a circular die, at a high temperature of 115 캜 by using an extruder having a molding temperature of 150 to 220 캜.

Example  2

Example 1 was repeated except that the content of (a) crystalline propylene-ethylene-1-butene random copolymer was 93% by weight and (b) propylene-ethylene-1-butene elastomer was 4% And the film was prepared in the same manner as in (1).

Example  3

Example 1 was repeated except that the component content was adjusted to (a) 87% by weight of crystalline propylene-ethylene-1-butene random copolymer and (b) 10% by weight of propylene- And the film was prepared in the same manner as in (1).

Comparative Example  One

A film was prepared in the same manner as in Example 1, except that (b) a propylene-ethylene-1-butene elastomer (ethylene content: 10 mol%, 1-butene content: 25 mol%) was used in Example 1.

Comparative Example  2

A film was prepared in the same manner as in Example 2, except that (b) a propylene-ethylene-1-butene elastomer (ethylene content 10 mol%, 1-butene content 25 mol%) was used in Example 2.

Comparative Example  3

A film was prepared in the same manner as in Example 3, except that (b) a propylene-ethylene-1-butene elastomer (ethylene content 10 mol%, 1-butene content 25 mol%) was used in Example 3.

Comparative Example  4

Example 1 was repeated except that (b) the propylene-ethylene-1-butene elastomer was not used and (a) the content of the crystalline propylene-ethylene-1-butene random copolymer was adjusted to 97 wt% 1, a film was prepared.

Test Example

The properties of the films prepared according to Examples and Comparative Examples were evaluated according to the following methods, and the results are shown in Table 1 below.

[Assessment Methods]

1) Shrinkage rate: The shrinkage rate was measured by measuring the length of the film dipped in 100, 130 and 150 ° C oil for 3 seconds after measuring a length of 10 cm × 10 cm.

2) Thermal Adhesion Strength: Two sheets of film were superimposed and heat-sealed at a temperature of 130 to 136 ° C under a sealing pressure of 2 kg / cm 2 for 1 second and a size of 1 cm × 2 cm. Loss force was measured.

3) Haze: An indicator of transparency of the film was measured by a flow chart of a 20 탆 stretched film based on ASTM D-1003 method.

Referring to Table 1, a crystalline propylene-ethylene-1-butene random copolymer and a propylene-ethylene-1-butene random copolymer prepared using the same polymerization reactor and the same propylene, ethylene and 1-butene feedstock in accordance with the present invention It can be confirmed that the heat-bonding strength is maximized without decreasing the transparency and the shrinkage ratio in the case of the film prepared by including the optimum content of each component having specific physical properties including

While the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, Such modifications and changes are to be considered as falling within the scope of the following claims.

Claims (6)

The following components are mixed in a mixer and extruded by an extruder to produce a polypropylene resin composition.
(a) propylene, ethylene, and 1-butene are used as raw materials, which are prepared in a polymerization reactor and introduced into a mixer, wherein the propylene component contains 1 to 10 mol% of ethylene and 1 to 10 mol% of 1-butene, , 2.16 kg load) of 3 to 10 g / 10 min and a melting temperature of 135 캜 or lower; more than 85% by weight and not more than 97% by weight of crystalline propylene-ethylene-1-butene random copolymer;
(b) an elastomer produced in the same polymerization reactor using the same raw material as the raw material (a) and introduced into the mixer, wherein the elastomer comprises 1 to 30 mol% of ethylene in the propylene component in order to improve the heat bonding strength without lowering transparency and shrinkage, And 2 to 10% by weight of a crystalline amorphous polypropylene resin composition containing 40 to 70 mol% of 1-butene and having a melt index (230 DEG C, 2.16 kg load) of 1 to 10 g / 10 min;
(c) 1 to 5% by weight of a mixed resin of low density polyethylene and linear low density polyethylene;
(d) 0.01 to 0.5 parts by weight of a slip agent based on 100 parts by weight of the total of the components (a) to (c); And
(e) 0.01 to 0.5 parts by weight of an anti-blocking agent per 100 parts by weight of the components (a) to (c). delete delete The method according to claim 1,
The mixed resin (c) contains 20 to 30% by weight of the low density polyethylene and 70 to 80% by weight of the linear low density polyethylene, and has a melt index (190 캜, 2.16 kg load) of 10 to 15 g / 10 min and a density of 0.920 To 0.925 g / cm < 3 >. The method according to claim 1,
The slip agent may be selected from the group consisting of erucamide, oleamide, behenamide stearamide, stearyl stearamidel, stearyl erucamide, And at least one amide-based slipping agent selected from the group consisting of oleyl palmitate amide. The method according to claim 1,
Wherein the anti-blocking agent is silica or zeolite.