KR101831529B1 - Expanded polypropylene resin composition and molded article prepared therefrom - Google Patents

Abstract

Disclosed are a bead expanded polypropylene resin composition which can be molded at low pressure while forming a uniform foam and has reduced molding time, and a molded article prepared therefrom. The expanded polypropylene resin composition comprises: (a) 100 parts by weight of a propylene-ethylene random copolymer of which the melting index (230°C, 2.16kg) is 24-40 g/10min; (b) 0.1-0.5 part by weight of a UV stabilizer; (c) 0.1-0.5 part by weight of silica powder; (d) 0.05-0.3 part by weight of a foam controller; and (e) 0.05-0.2 part by weight of a processing stabilizer.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a polypropylene resin composition for foaming, and a molded article produced from the same. BACKGROUND ART [0002]

The present invention relates to a polypropylene resin composition for foaming and a molded article produced therefrom, and more particularly to a polypropylene resin composition for bead foaming with improved formability and a molded article produced using the same.

In general, polyurethane, polyolefin, PVC, and ABS resin are used in the foamed products, but the most commonly used products are polystyrene. These polystyrene products have a high elastic modulus, excellent heat insulation properties, and can be foamed by light-weight expansion through high-expansion foam molding, which is widely applied to food containers and the like. However, recently, food containers using polystyrene products have been replaced by paper containers due to the problem of environmental hormones occurring in food containers.

In order to solve the above-mentioned problems, polypropylene resin is foamed to be widely used for food packaging containers and architectural use. Polypropylene is most widely used as packaging material for food packaging films because it does not contain harmful substances to human body. Foamed food packaging containers are also expected to grow gradually.

However, in order to improve the heat resistance and the heat insulating property of the polypropylene product, it is necessary to use a product having a high heat resistance. In addition to this, the product requires a lot of energy to press the packaging container after the foaming, On the other hand, when a product having a low heat resistance is used to improve the productivity of a product, it takes a long time to make a crystal, and thus it takes a long time to perform a pressing process on the packaging container.

On the other hand, there is a method of physically blending polyethylene with a polypropylene having a very low melt index. However, when the polyethylene is blended with the polypropylene as described above, there arises a problem in uniformity of the product, and it is difficult to form a uniform foam.

Korean Patent Laid-Open Publication No. 2013-0002957 discloses a polypropylene resin using a dual random copolymer in order to improve the foaming property of polypropylene. In this case, the foamed cell has excellent stability, high heat resistance and rigidity, The welding pressure of the bead and the use time of the steam can not be lowered, which makes it difficult to reduce the energy.

Korean Patent Publication No. 1999-0009304 discloses a resin which provides polypropylene resin expanded particles having equivalent properties by in-mold molding at a low heating temperature using a propylene-ethylene-butene-1 ternary random copolymer, In this case, using ethylene and butene-1, the impact strength is superior to that of the conventional product, but the stiffness is weaker than that of the conventional random copolymer foam product.

Korean Patent Laid-Open Publication No. 2011-0085443 discloses a resin that provides a foamed article having excellent fusion bonding property by applying a beta nucleating agent to a polypropylene resin for foamed beads in order to improve melt adhesion. However, in this case, And it is difficult to reduce cost and energy by applying expensive beta nucleating agent.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a polypropylene resin composition for foaming beads which can be molded at a low pressure while shortening a molding time while forming a uniform foam, and a molded article produced therefrom will be.

(A) 100 parts by weight of a propylene-ethylene random copolymer having a melt index (230 DEG C, 2.16 kg) of 24 to 40 g / 10 min; (b) 0.1 to 0.5 parts by weight of an ultraviolet stabilizer; (c) 0.1 to 0.5 parts by weight of a silica powder; (d) 0.05 to 0.3 parts by weight of a foam controlling agent; And (e) 0.05 to 0.2 parts by weight of a processing stabilizer.

The propylene-ethylene random copolymer has a weight average molecular weight of 150,000 to 190,000 g / mol.

Also, the propylene-ethylene random copolymer has a content of ethylene comonomer of 0.5 to 10% by weight.

Also, the foam controlling agent is at least one selected from the group consisting of zinc borate, zinc metaborate, and basic zinc borate.

Wherein the processing stabilizer is a complex of magnesium hydroxystearate and polyoxyethylene.

According to another aspect of the present invention, there is provided a foamed bead foamed article comprising the above polypropylene resin composition.

And the molded article is a shock absorbing article.

According to the present invention, by mixing an ultraviolet stabilizer, a silica powder, a bubble regulator and a processing stabilizer with an optimal composition in a propylene-ethylene random copolymer having an optimum melt index, it is possible to perform molding under low pressure, It is possible to provide a polypropylene resin composition having a foam.

Further, the polypropylene resin composition according to the present invention can be effectively used for manufacturing plastic articles for impact-absorbing materials through bead fusion.

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) 100 parts by weight of a propylene-ethylene random copolymer having a melt index (230 DEG C, 2.16 kg) of 24 to 40 g / 10 min; (b) 0.1 to 0.5 parts by weight of an ultraviolet stabilizer; (c) 0.1 to 0.5 parts by weight of a silica powder; (d) 0.05 to 0.3 parts by weight of a foam controlling agent; And (e) 0.05 to 0.2 parts by weight of a processing stabilizer; and a molded article produced from the polypropylene resin composition.

The present invention relates to a conventional polypropylene resin composition for foaming foam, which can be fused at a low temperature and a low pressure in a fusion step after foam foaming, and can reduce the use time of the steam used during fusion and the molding pressure to reduce energy . In addition, by adding a UV stabilizer, a silica powder, a bubble controlling agent and a processing stabilizer to the non-uniformity of the expanded particles, which may cause problems in the bead foaming and fusion bonding steps, a polypropylene resin composition having uniform expanded particles is obtained, A molded article to be applied as a shock absorbing product can be provided.

Hereinafter, each constitution of the polypropylene resin composition according to the present invention will be described in detail.

(a) a propylene-ethylene random copolymer

In the present invention, the propylene-ethylene random copolymer may be prepared by a commonly known process. For example, a propylene monomer and an ethylene monomer may be added to a polymerization reactor, triethylaluminum, diisocyanate and a silane-based electron donor may be introduced, and slurry bulk polymerization may be carried out at a reaction temperature of 65 to 75 ° C and a pressure of 32 to 34 atm . However, as other usable catalysts in the production of the above-mentioned propylene-ethylene random copolymer, a phthalate catalyst and a succinate catalyst may be used, and thus the catalyst is not limited to a diisocyanate catalyst.

In the present invention, the melt index of the propylene-ethylene random copolymer is preferably 24 to 40 g / 10 min at 230 ° C. and 2.16 kg, and preferably 24 to 28 g / 10 min depending on a molding machine for molding the product. If the melt index is less than 24 g / 10 min, the bead foaming is good, but it is difficult to form at a low pressure in the fusion step and the amount of steam used is increased, and the fusing strength is lowered at low temperature and low pressure molding. If the melt index exceeds 40 g / 10 min, the foamed particles are not uniformly produced and bead foaming is difficult.

The weight average molecular weight of the propylene-ethylene random copolymer may be 150,000 to 190,000 g / mol, and preferably 180,000 to 190,000 g / mol. When the weight average molecular weight is less than 150,000 g / mol, the molecular weight is too small to foam smoothly. If the weight average molecular weight is more than 190,000 g / mol, the polymer chains are not sufficiently melted at the low pressure, Can be lowered.

The ethylene comonomer content of the propylene-ethylene random copolymer may be from 0.5 to 10% by weight, and preferably from 2 to 5% by weight. When the content of the ethylene comonomer is less than 0.5% by weight, the softness is insufficient, so that the expanded particles may not be formed well when the beads are foamed. When the content is more than 10% by weight, it may be difficult to produce the resin composition by the polymerization process.

(b) Ultraviolet stabilizer

In the present invention, the ultraviolet light stabilizer prevents ultraviolet light from interrupting the molecular chains of the resin due to ultraviolet rays while preventing ultraviolet light from absorbing and interfering with the ultraviolet light. The ultraviolet light stabilizer may be a product not containing a benzene ring.

As the ultraviolet stabilizer, conventional components known in the art can be used without limitation. Non-limiting examples of ultraviolet stabilizers that can be used include polymers of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidine- 2,2,6,6-tetramethyl-1-piperidine-ethanol product, bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacate (Bis -tetramethyl-4-piperidinyl sebacate, poly [[6- [(1,1,3,3-tetramethylbutyl) amino] -1,3,5-triazine-2,4- , 2,6,6-tetramethyl-4-piperidinyl] imino] -1,6-hexanediyl [(2,2,6,6-tetramethyl-4- piperidinyl) imino]] Poly [[6 - [(1,1,3,3-tetramethylbutyl) amino] -1,3,5-triazine-2,4-diyl] - [2,2,6,6-tetramethyl- imino] -1,6-hexanediyl [(2,2,6,6-tetramethyl-4-piperidinyl) imino]], etc. These may be used alone or in combination of two or more.

The ultraviolet stabilizer is used in an amount of 0.1 to 0.5 parts by weight based on 100 parts by weight of the propylene-ethylene random copolymer. If the content of the ultraviolet stabilizer is less than 0.1 parts by weight, the stabilizer performance against ultraviolet rays may not be exhibited. If the content of the ultraviolet stabilizer exceeds 0.5 parts by weight, the ultraviolet stabilizer may not be further improved.

(c) a silica powder

In the present invention, the silica powder plays a role in helping the nucleation of the polymer material to be advantageous, and thus functions to help the cell structure uniformity in the foaming molding.

As the silica powder, any conventional silica known in the art may be used without limitation. For example, porous white amorphous silica having a particle size of 4.0 to 4.8 탆 and a pore volume of 0.6 to 0.8 ml / g, The content of SiO ₂ is preferably 99% or more. Further, it is preferable to use silica having a water content of less than 2% when dried at 160 ° C.

The silica powder is used in an amount of 0.1 to 0.5 parts by weight based on 100 parts by weight of the propylene-ethylene random copolymer. If the content of the silica powder is less than 0.1 part by weight, the uniformity of the foamed cells may deteriorate. If the amount of the silica powder is more than 0.5 parts by weight, the added silica particles may aggregate due to the dispersion failure.

(d)

In the present invention, the bubble controlling agent functions to uniformly maintain the size of the expanded particles during bead foaming and bead fusion.

As the bubble regulator, any conventional components known in the art can be used without limitation. Non-limiting examples of usable foam modifiers include powders such as zinc borate, zinc metaborate, and basic zinc borate.

The foam modifier powder is used in an amount of 0.05 to 0.3 parts by weight based on 100 parts by weight of the propylene-ethylene random copolymer. If the amount of the bubbling agent powder is less than 0.05 part by weight, the uniformity of the foamed cells may deteriorate. If the amount of the bubbling agent powder is more than 0.3 part by weight, .

(e) Processing stabilizer

In the present invention, the processing stabilizer can prevent the die lip build-up when the resin is extruded into mini-pellets to produce expanded particles, and the die lip build-up can be improved to keep the size and appearance of the bead foam uniform have. And also has the function of improving the processing stability by facilitating the flowability of the resin composition.

As the processing stabilizer, a magnesium organic complex can be used, and a composite having a composition ratio of 85 to 95% by weight of magnesium hydroxystearate and 5 to 15% by weight of polyoxyethylene can be used.

The process stabilizer is used in an amount of 0.05 to 0.2 parts by weight based on 100 parts by weight of the propylene-ethylene random copolymer. If the content of the processing stabilizer is less than 0.05 part by weight, the build up of the die lip increases, and the size and appearance of the bead foam are not uniform, resulting in a problem that the uniformity of appearance of the final molded product is lowered. There is a problem in that the performance improvement is not achieved.

The polypropylene resin composition according to the present invention may further contain one or more conventional additives known in the art as other additives such as an antioxidant, a neutralizing agent, an antistatic agent, a heat stabilizer, and a slip agent. The content of these additives may be 0.01 to 1 part by weight based on 100 parts by weight of the polypropylene resin composition of the present invention, but is not particularly limited thereto.

The antioxidant is capable of preventing the resin molecules from being broken by heat, oxygen, or the like when the product is manufactured using the polypropylene resin composition. The neutralizing agent can be removed by the residue (metal component) It is possible to neutralize an acid (concretely, hydrogen chloride) which can be generated. The antistatic agent is capable of reducing the generation of static electricity in a product produced using the polypropylene resin composition.

The preparation of the polypropylene resin composition according to the present invention is not particularly limited and can be produced by a conventional method known in the art. As a preferable example, the raw material components are put into a Henschel mixer, mixed sufficiently, molded at an extruder molding temperature of 160 to 230 DEG C, and made into a polypropylene mini pellet using a 40 mm coaxial twin-screw extruder having an L / D of 25 .

Meanwhile, the production of the foam using the polypropylene resin composition according to the present invention can be carried out according to a conventional method in the art, for example, by the following method. That is, 100 kg of the resin composition and 220 kg of water were charged into an autoclave reactor equipped with a stirrer, 10 kg of carbon dioxide gas as a blowing agent was added to the autoclave reactor, and the reactor was reacted at 135 ° C with stirring at 28 bar. At this time, the expansion ratio can be set to 15 times. The thus-reacted expanded particles are filled in a flat metal mold having a width of 210 mm, a length of 2700 mm and a thickness of 100 mm, and subjected to melt compression using water vapor to produce a final product.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. However, the following examples are illustrative of the present invention, and the present invention is not limited to the examples described below.

Example  One

(a) 100 parts by weight of a propylene-ethylene random copolymer having a melt index of 24 g / 10 min at 230 DEG C and 2.16 kg, a weight average molecular weight of 190,000 g / mol and an ethylene comonomer content of 4.0 wt% 0.3 part by weight of a UV stabilizer (Dimethyl succinate polymer with 4-hydroxy-2,2,6,6-tetramethyl-1-piperidine-ethanol), (c) porous silica (particle size 4.2 to 4.6 탆, pore volume 0.6 to 0.8 ml / g, SiO ₂ content of more than 99%, less than the content of 2% of water when dried at 160 ℃) 0.3 parts by weight, (d) foam control agent (zinc borate), 0.1 part by weight, and (e) processing stabilizer (hydroxy magnesium stearate 90% by weight and polyoxyethylene 10% by weight composite) was prepared, and then the foamed body was formed by the above-mentioned method using the resin composition thus prepared.

Example  2

A propylene-ethylene random copolymer having a melt index of 28 g / 10 min and a weight average molecular weight of 180,000 g / mol was used in Example 1, (b) 0.4 part by weight of an ultraviolet stabilizer, (c) 0.4 part by weight And (d) the bubble controlling agent was adjusted to a content of 0.2 part by weight.

Example  3

A foam was formed in the same manner as in Example 1 except that (a) a propylene-ethylene random copolymer having an ethylene comonomer content of 3.5 wt% was used in Example 1.

Comparative Example  One

A foam was formed in the same manner as in Example 1, except that (a) a propylene-ethylene random copolymer having a melt index of 10 g / 10 min and a weight average molecular weight of 240,000 g / mol was used in Example 1.

Comparative Example  2

A foam was formed in the same manner as in Example 1, except that (d) the bubble controlling agent was adjusted to 0.01 part by weight in Example 1.

Comparative Example  3

A foam was formed in the same manner as in Example 1, except that (c) the content of the porous silica was adjusted to 0.01 part by weight in Example 1.

Comparative Example  4

A foam was formed in the same manner as in Example 1, except that (d) the bubble controlling agent was adjusted to 1.0 part by weight in Example 1.

Comparative Example  5

A foam was formed in the same manner as in Example 1 except that (e) a processing stabilizer was not used in Example 1.

Test Example

The properties of the foams prepared in the above Examples and Comparative Examples were evaluated by the following methods, and the results are shown in Table 1 below.

[Property evaluation method]

1) Bead cell structure: The cell size of foamed particles was compared. The evaluation criteria are as follows.

⊚: A generally uniform bead (Cell: 200 to 400 탆)

?: Large size distribution (Cell: 100 to 450 占 퐉)

?: Small overall (Cell: 150 占 퐉 or less)

×: coexistence of large and small (Cell: 1 to 500 μm)

2) Molding pressure: The foamed particles were placed in a mold and steam was sprayed to compare the steam pressure. The evaluation criteria are as follows.

◎: molding pressure less than 2.1 bar

○: molding pressure 2.1 bar to 2.4 bar

?: Molding pressure of 2.4 bar or more to less than 2.7 bar

X: molding pressure 2.7 bar or more

3) Molding speed: The foamed particles were placed in a product mold and steam injection was performed to compare the molding speed. The evaluation criteria are as follows.

◎: steam time less than 28 seconds

○: Steam time 28 seconds to less than 32 seconds

△: Steam time from 32 seconds to less than 36 seconds

×: Steam time 36 seconds or more

4) Compressive Strength: Compressive strengths of 10 cm x 10 cm were compared to fused molded foams, and their evaluation criteria are as follows.

?: 4.0 MPa or more

○: 3.5 MPa or more and less than 4.0 MPa

?: 3.0 MPa or more and less than 3.5 MPa

X: less than 3.0 MPa

5) Appearance: Appearance of the molded products subjected to fusion-molding was compared, and the evaluation criteria thereof are as follows.

◎: The surface is smooth and the product is uniform without distortion

○: There are some defective molding spots on the surface but the product is uniform without distortion

△: There is some defective molding spot on the surface, but the product is uniform without distortion

X: There are some defective molding spots on the surface, and the product is warped.

As shown in Table 1, when the ultraviolet stabilizer, the silica powder, the air bubble modifier, and the processing stabilizer were mixed with the propylene-ethylene random copolymer having the optimum melt index according to the present invention in an optimum composition (Examples 1 to 3) Compared with the comparative examples 1 to 5, the molding pressure and the steam consumption amount are reduced, which is advantageous for energy saving and has excellent physical properties.

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 (7)

(a) 100 parts by weight of a propylene-ethylene random copolymer having a melt index (230 DEG C, 2.16 kg) of 24 to 28 g / 10 min;
(b) 0.1 to 0.5 parts by weight of an ultraviolet stabilizer;
(c) 0.1 to 0.5 parts by weight of a silica powder;
(d) 0.05 to 0.3 parts by weight of a foam controlling agent; And
(e) 0.05 to 0.2 parts by weight of a processing stabilizer;
A polypropylene resin composition for foaming,
The propylene-ethylene random copolymer preferably has an ethylene comonomer content of 2 to 5% by weight,
Wherein the processing stabilizer is a complex of magnesium hydroxystearate and polyoxyethylene. The method according to claim 1,
Wherein the propylene-ethylene random copolymer has a weight average molecular weight of 150,000 to 190,000 g / mol. delete The method according to claim 1,
Wherein the foam controlling agent is at least one selected from the group consisting of zinc borate, zinc metaborate and basic zinc borate. delete A molded article obtained by foaming a bead with the polypropylene resin composition according to claim 1. The method according to claim 6,
Wherein the molded article is a shock absorbing article.