KR102201977B1 - Brenched polypropylene resin, preparing method of the same and foamed article comprising the same - Google Patents

Abstract

(A) In an inert atmosphere, a linear polypropylene resin having a melt index of 0.1 g/10min or more and 10.0 g/10min or less, measured according to ASTM D1238, and an organic peroxide having a half-life of 120°C of 1 second or less, is prepared from 70°C to 110°C. Stirring at the following temperature; And (b) following step (a), reacting at a temperature of 150° C. or more and 230° C. or less; including, a method for producing a branched polypropylene resin and a branched polypropylene resin prepared using the same, including It relates to a foam.

Description

Branched polypropylene resin, its manufacturing method, and foam comprising the same {BRENCHED POLYPROPYLENE RESIN, PREPARING METHOD OF THE SAME AND FOAMED ARTICLE COMPRISING THE SAME}

The present invention relates to a branched polypropylene resin, a method for producing the same, and a foam comprising the same.

In general, polypropylene resins have excellent molding processability and chemical resistance, are relatively excellent in tensile strength, flexural strength, and rigidity, and are also inexpensive, so they are applied to various applications such as injection and extrusion. However, the polypropylene resin has a low melt tension and is difficult to apply to various molding processes such as a large vacuum/pressure molding process, a foaming process, and an extrusion coating molding process that require high melt tension.

In order to improve the molding processability of such a polypropylene resin, a method of mixing polypropylene with polyethylene is known, but the degree of improvement in molding processability is not satisfactory, so a large amount of polyethylene is required, and thus, there is a problem that the strength of the resulting mixture decreases. .

In addition, there are attempts to improve the melt tension by increasing the molecular weight of polypropylene, but the high molecular weight has a problem in that the melt flowability, which is one variable in the molding processability, decreases, and an appropriate balance between the melt tension and the melt flowability cannot be maintained. .

In the paper of Andre H. Hogt and Wim K. Frijlink, NEW HIGH-MELT-STRENGTH POLYPROPYLENE BY REACTIVE RXTRUSION, the effect of polymer branching is disclosed. Specifically, this paper describes the change in the branching structure due to the generation of radicals of polyolefins due to the reaction temperature conditions in consideration of the half-life of the organic peroxide, the effect of the content with the polyolefin requiring modification, and the post-treatment process for unreacted products after the reaction. It presents a lot of change.

Therefore, it is necessary to consider specific conditions and a manufacturing method for generating a branched structure of polypropylene to improve the properties of the polypropylene resin.

The present invention is to provide a method for producing a branched polypropylene resin and a branched polypropylene resin prepared using the same. Furthermore, it is intended to provide a foam comprising the branched polypropylene resin.

In an exemplary embodiment of the present invention, (a) a linear polypropylene resin having a melt index of 0.1 g/10min or more and 10.0 g/10min or less, measured according to ASTM D1238 under an inert atmosphere, and an organic peroxide having a 120°C half-life of 1 second or less. Stirring at a temperature of 70° C. or more and 110° C. or less; And (b) reacting at a temperature of 150° C. or more and 230° C. or less, following step (a), to provide a method for producing a branched polypropylene resin.

Another exemplary embodiment of the present invention is prepared according to the above manufacturing method, and the melt extensibility of v120 measured according to ISO 16790:2005 is 200 ㎜/s or more and 250 ㎜/s or less, and the F120 melt tension is 20 cN or more and 35 cN. The following, a branched polypropylene resin is provided.

Another exemplary embodiment of the present invention provides a foam comprising the branched polypropylene resin and having a foam density of 0.4 g/cm 3 or less.

The branched polypropylene resin manufactured by the manufacturing method according to an exemplary embodiment of the present invention has high melt extensibility and melt tension, and thus, improved extrusion foaming performance can be implemented. Furthermore, since the foam containing the branched polypropylene resin has a low foam density, there is an advantage that can be applied to various products.

1 is a graph measuring melt extensibility (v120) and melt tension (F120) according to Example 1, Comparative Example 1, and Comparative Example 2.
2 is a graph measuring melt extensibility (v120) and melt tension (F120) according to Example 1, Comparative Example 1, and Comparative Examples 3 to 5.

In the present specification, when a part "includes" a certain component, it means that other components may be further included rather than excluding other components unless otherwise stated.

In the present specification, the unit "parts by weight" may mean a ratio of weight between each component.

In the present specification, the weight average molecular weight (g/mol) may be a converted value for polystyrene measured by gel permeation chromatography (GPC).

In general, the high crystallinity of polypropylene resin has a high melting temperature, low density, high stiffness, high impact, high chemical resistance, and high moisture barrier properties, whereas a decrease in elongation due to low melt tension requires a deep deep bridge ratio. Its use is limited in the production of thermoformed products, blow molding, high-speed extrusion coating, and foam materials. The characteristic of the polypropylene resin is that its structure is linear, and this problem can be solved by introducing a branched chain into the main chain. The branched polypropylene resin can reduce uneven thickness of the sheet stretched in thermoforming and reduce pinholes on the sheet surface. Furthermore, it can improve the sagging phenomenon of the parison due to gravity in blow molding, and can play a role of drastically reducing the neck-in phenomenon during film extrusion. In addition, it has a wide foaming temperature condition in extrusion foaming, and can help uniform cell growth inside the foaming cell. Polypropylene with increased melt tension is characterized by introducing long chain branching (LCB) into the main chain and having a high molecular weight and a broad molecular weight distribution. This is called high melt tension polypropylene. The production method of high melt tension polypropylene that can be commercially produced includes 1) polymerization method 2) electron beam irradiation method 3) reaction extrusion method. Among them, the addition of the branched chain by reaction extrusion method mainly starts from the formation of polypropylene radicals in organic peroxides. In many patents, the organic peroxide for decomposing the linear chain structure of polypropylene has a half-life of 90°C to 200°C for 10 hours, and different types of organic peroxides having different half-lives are sequentially introduced to promote recombination of the polypropylene chains.

As a result of continuing research on branched polypropylene resins with improved physical properties, the present inventors have found that when a predetermined organic peroxide and a linear polypropylene resin are mixed at a specific temperature and then reacted, a branched type having high melt elongation and melt tension It was discovered that polypropylene resin was produced, and the present invention was completed.

Hereinafter, the present invention will be described in detail.

In an exemplary embodiment of the present invention, (a) a linear polypropylene resin having a melt index of 0.1 g/10min or more and 10.0 g/10min or less, measured according to ASTM D1238 under an inert atmosphere, and an organic peroxide having a 120°C half-life of 1 second or less. Stirring at a temperature of 70° C. or more and 110° C. or less; And

(b) following step (a), reacting at a temperature of 150° C. or more and 230° C. or less; and a method for producing a branched polypropylene resin is provided.

The method for producing a branched polypropylene resin according to the present invention includes the step of stirring the linear polypropylene according to step (b) before the reaction with the organic peroxide under a temperature of 70° C. or higher and 110° C. and an inert atmosphere. Characterized in that. The organic peroxide may cause the polymer chain to break rapidly at a temperature equal to or higher than the melting temperature of the polypropylene resin. Therefore, in the present invention, by adding the step of stirring the linear polypropylene resin and the organic peroxide in a low temperature and inert atmosphere as in step (a), it is possible to minimize the polymer chain breakage caused by the organic peroxide. Specifically, step (a) may be impregnating the linear polypropylene resin with the organic peroxide. When the stirring temperature in step (a) is less than 70° C. or more than 110° C., the melt elongation and melt tension of the branched polypropylene resin to be produced are not sufficiently high, and thus the foam density of the foam using the same may be too high. In addition, even when step (a) is omitted and a branched polypropylene resin is prepared by reacting linear polypropylene and organic peroxide, the melt extensibility and melt tension are not sufficiently high, so the foam density of the foam using the same may be too high. .

According to an exemplary embodiment of the present invention, steps (a) and (b) may be performed in an atmosphere in which an active gas such as oxygen is not substantially present. Specifically, steps (a) and (b) may create an inert atmosphere by purging with nitrogen.

The organic peroxide decomposes the linear chain structure of the linear polypropylene and induces recombination thereof, thereby making it possible to prepare a branched polypropylene. Further, since the organic peroxide has a very short half-life of less than 1 second at 120° C., there is an advantage of minimizing a polymer chain break. That is, when an organic peroxide having a half-life of 120° C. of more than 1 second is used, a polymer chain breaking phenomenon continuously occurs due to a relatively long half-life, which may lead to deterioration of the properties of the final branched polypropylene.

According to an exemplary embodiment of the present invention, the organic peroxide may be peroxydicarbonate. Specifically, the organic peroxide is di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-n-butyl peroxydicarbonate ), di-sec-butyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, isopropyl-sec- Butyl peroxydicarbonate (isopropyl-sec-butyl peroxydicarbonate), di-2-ethylhexyl peroxydicarbonate (di-2-ethyhexyl peroxydicarbonate), di-3-methoxybutyl peroxydicarbonate (di-3-methoxybutyl peroxydicarbonate), Di-2-phenoxyethyl peroxydicarbonate, dimyristyl peroxydicarbonate, dicetyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, and Di (4-t-butyl cyclohexyl) peroxydicarbonate (di (4-t-butyl cyclohexyl) peroxydicarbonate) may include at least one selected from the group consisting of.

According to an exemplary embodiment of the present invention, the content of the organic peroxide may be 0.1 parts by weight or more and 5 parts by weight or less based on 100 parts by weight of the linear polypropylene resin. Specifically, the content of the organic peroxide may be 0.2 parts by weight or more and 4 parts by weight or less, or 0.5 parts by weight or more and 3.5 parts by weight or less based on 100 parts by weight of the linear polypropylene resin.

When the content of the organic peroxide is less than the above range, the generation of radicals of the linear polypropylene is reduced, thereby reducing the Z-average molecular weight, and when the content of the organic peroxide exceeds the above range, the produced branched polypropylene is used. There is a problem that the number average molecular weight (Mn) may decrease as decomposition.

According to an exemplary embodiment of the present invention, the stirring time in step (a) may be 30 minutes or more and 1 hour or less. When the stirring time in step (a) is less than 30 minutes, the linear polypropylene and the organic peroxide are not sufficiently mixed, so that the effect of reducing the above-described polymer chain breakage phenomenon may not be sufficiently implemented. In addition, when the stirring time in step (a) exceeds 1 hour, a problem in which polymer chain breakage may occur due to excessive reaction may occur.

According to an exemplary embodiment of the present invention, the linear polypropylene resin may be a linear polypropylene homopolymer and/or a copolymer of polypropylene and ethylene.

According to an exemplary embodiment of the present invention, the melt index measured according to ASTM D1238 of the linear polypropylene resin may be 0.1 g/10min or more and 10.0 g/10min or less. When the melt index of the linear polypropylene is within the above range, molding is easy due to proper flowability, and further, high physical properties of the manufactured branched polypropylene can be realized.

According to an exemplary embodiment of the present invention, the number average molecular weight (Mn) of the linear polypropylene resin may be 50,000 g/mol to 120,000 g/mol. In addition, the weight average molecular weight (Mw) of the linear polypropylene resin may be 200,000 g/mol to 500,000 g/mol, and further, the Z-average molecular weight (Mz) of the linear polypropylene resin is 500,000 g/mol to 1,000,000 It can be g/mol. When the linear polypropylene resin has a molecular weight range as described above, physical properties of a molded article using the branched polypropylene to be produced can be greatly improved due to a wide molecular weight distribution and a high molecular weight in the polymer region. In particular, when the molded article to be manufactured is a foam, it has a high melt tension due to the above characteristics, and thus a low foam density can be realized.

According to an exemplary embodiment of the present invention, step (b) may be to react by further including an antioxidant. The antioxidant may play a role of controlling the activity of the organic peroxide. Specifically, since the organic peroxide can decompose the produced branched polypropylene resin to reduce the melt tension, an antioxidant is added to control the activity of the organic peroxide after the reaction to prevent the decomposition of the branched polypropylene. Can be prevented.

According to an exemplary embodiment of the present invention, the antioxidant may be added in an amount of 0.05 parts by weight to 0.2 parts by weight based on 100 parts by weight of the linear polypropylene resin. In addition, the antioxidant may be added with 0.05 parts by weight to 0.1 parts by weight of a neutralizing agent based on 100 parts by weight of the linear polypropylene resin. When the antioxidant and/or neutralizing agent are added within the above range, the branched polypropylene having a high melt tension can be prepared by minimizing the decomposition of the branched polypropylene by the organic peroxide after the reaction.

According to an exemplary embodiment of the present invention, the antioxidant may include a primary antioxidant and a secondary antioxidant. Specifically, the primary antioxidant may be added at the beginning of step (b). Specifically, the primary antioxidant may be added in an amount of 0.05 parts by weight to 0.2 parts by weight based on 100 parts by weight of the linear polypropylene resin at the start of step (b). When the content of the primary antioxidant is less than the above range, the molecular weight of the branched polypropylene resin to be produced may be lowered, and when added in excess of the above range, the generation of radicals may decrease and the conversion rate may decrease.

In addition, the secondary antioxidant may be added during the reaction of step (b). Specifically, the secondary antioxidant may be added in an amount of 0.05 parts by weight to 0.2 parts by weight based on 100 parts by weight of the linear polypropylene resin at the start of step (b). When the content of the secondary antioxidant is less than the above range, the branched polypropylene to be produced may be decomposed to reduce the molecular weight, and when the amount is added in excess of the amount added, the chromaticity decreases due to the incorporation of the antioxidant or the melt tension Decreases can occur. In addition, the second antioxidant is preferably added when 70% to 95% of the conversion reaction is in progress, more preferably 80% to 95%, most preferably 88% to 93% of the reaction I can. When the conversion reaction proceeds less than 70%, when the second antioxidant is added, the conversion rate may decrease, and when the conversion reaction is added when the conversion reaction exceeds 95%, the effect of the antioxidant may decrease.

The first antioxidant and the second antioxidant may be added together with a neutralizing agent. In this case, the amount of the neutralizing agent added may be 0.05 parts by weight to 0.1 parts by weight based on 100 parts by weight of the linear polypropylene resin.

According to an exemplary embodiment of the present invention, step (b) may be performed using reaction extrusion. Specifically, the extruder for performing step (b) requires an extruder with a long L/D to sufficiently react the organic peroxide, and may be a twin-screw extruder having a minimum L/D of 35 or more. This can be manufactured using a kneader, a Banbury mixer, a single screw compressor, etc. in addition to the twin screw extruder used for the melt reaction, but a twin screw extruder is used to simultaneously obtain excellent reactivity and high productivity. It is desirable.

In addition, the extruder may be provided with at least one side feeder for side feeding the second antioxidant. When using a twin-screw extruder, the melting reaction temperature is preferably set to 160°C or more and 230°C or less. This is because the linear polypropylene mixture is sufficiently reacted/kneaded in the above temperature range, and the organic peroxide as an initiator reacts completely with the linear polypropylene to obtain a branched polypropylene having no residual amount. When using a twin-screw extruder, a suitable temperature gradient can be created by appropriately adjusting each temperature controller from the feeding zone entrance to the outlet at the front end of the extruder.

According to another exemplary embodiment of the present invention, the melt extensibility of v120 manufactured according to the above manufacturing method and measured according to ISO 16790:2005 is 200 mm/s or more and 250 mm/s or less, and the F120 melt tension is 20 cN or more 35 A branched polypropylene resin having cN or less is provided.

According to an exemplary embodiment of the present invention, the shape of the branched polypropylene resin may be a strand shape, a sheet shape, a flat plate shape, or a pellet shape. The branched polypropylene can be processed by adding various additives depending on the application. The additives may include a modification additive, a colorant, and the like, and the modification additive may be a dispersant, a lubricant, a plasticizer, a flame retardant, an antioxidant, an antistatic agent, a light stabilizer and an ultraviolet absorber.

Since the branched polyolefin resin has improved melt elongation and melt tension, it has excellent processability such as vacuum formability, blow formability, foam formability, and calender formability, and thus has various uses. Specifically, since the branched polyolefin resin can realize a low foaming density when manufacturing a foam due to improved melt elongation and melt tension, it may be suitable for use as a foam.

Another exemplary embodiment of the present invention provides a foam comprising the branched polypropylene resin and having a foam density of 0.4 g/cm 3 or less. Specifically, the foam may be an extruded foam. Specifically, the foaming density of the foam may be 0.2 g/cm 3 or more and 0.4 g/cm 3 or less, specifically 0.2 g/cm 3 or more and 0.35 g/cm 3 or less.

Hereinafter, examples will be described in detail to illustrate the present invention in detail. However, the embodiments according to the present invention may be modified in various other forms, and the scope of the present invention is not construed as being limited to the embodiments described below. The embodiments of the present specification are provided to more completely describe the present invention to those of ordinary skill in the art.

[ Example One]

Powder-shaped linear polypropylene homopolymer (Mn: 60,000 g/mol, Mw: 300,000 g/mol, Mz: 800,000 g/mol) 100 parts by weight and 3 parts by weight of diisopropyl peroxydicarbonate in a 1 L reactor purged with nitrogen Stirred sufficiently for 1 hour at 80 °C temperature. Furthermore, the mixture stirred with 0.1 parts by weight of the first antioxidant was mixed with a twin-screw extruder (L/D 40, diameter 75 pie, K/B (Kneading block) 1% to 20%, extrusion temperature 160°C to 230°C, extrusion speed) 280 RPM to 350 RPM, feeding speed 20 kg/h to 40 kg/h, side feeding speed 1 kg/h to 10 kg/h, barrel temperature range 150° C. to 230° C.) and reacted, and the reaction was 90 When the% was completed, 0.1 parts by weight of the second antioxidant was added and then extruded to prepare a pellet (branched polypropylene resin). The pellets obtained after extrusion were sufficiently dried at 80° C. for 24 hours.

The prepared pellets were measured for melt extensibility (v120) and melt tension (F120) according to ISO 16790:2005(E).

Further, the produced pellets were subjected to a single-screw extruder (L/D 33, diameter 19 mm, 4 melting zones, static mixer (2 cooling zones), CO ₂ metering pump (1 ml/min), extrusion temperature 150 ℃ to 200 ℃, extrusion A foam was produced by extrusion foaming using a speed of 80 RPM to 100 RPM, and the foam density thereof was measured.

[ Comparative example One]

Pellets (linear polypropylene resin) were prepared using the linear polypropylene in Example 1 and the twin screw extruder in Example 1, and their melt extensibility (v120) and melt tension (F120) were measured. Further, a foam was prepared by the method of Example 1, and the foam density thereof was measured.

[ Comparative example 2]

A pellet (branched polypropylene resin) was prepared in the same manner as in Example 1, except that benzoyl peroxide was used instead of diisopropyldicarbonate as the organic peroxide, and its melt extensibility (v120) and melt tension (F120) Was measured. Further, a foam was prepared by the method of Example 1, and the foam density thereof was measured.

1 is a graph measuring melt extensibility (v120) and melt tension (F120) according to Example 1, Comparative Example 1, and Comparative Example 2. The results according to FIG. 1 and the foam density of the foam are summarized in Table 1 below.

division Stirring conditions PP structure Melt extensibility (v120)
(mm/s) Melt tension (F120)
(cN) Foam density
(g/cm3) Example 1 80 ℃ Branched 236 31 0.32 Comparative Example 1 - Linear 156 3.0 0.71 Comparative Example 2 80 ℃ Branched 259 0.9 0.78

According to the results of Table 1, it can be seen that Example 1 has excellent melt extensibility (v120) and melt tension (F120), and thus a low foam density can be implemented. Specifically, Comparative Example 1, which is a linear polypropylene resin, has low melt elongation (v120) and melt tension (F120), and Comparative Example 2 to which benzoyl peroxide is applied has excellent melt elongation (v120) but excessive melt tension. It can be seen that the foaming density is very high.

[ Comparative example 3]

A pellet (branched polypropylene resin) was prepared in the same manner as in Example 1, except that the stirring temperature in the reactor was adjusted to 65°C, and its melt elongation (v120) and melt tension (F120) were measured. . Further, a foam was prepared by the method of Example 1, and the foam density thereof was measured.

[ Comparative example 4]

A pellet (branched polypropylene resin) was prepared in the same manner as in Example 1, except that the stirring temperature in the reactor was adjusted to 120°C, and its melt elongation (v120) and melt tension (F120) were measured. . Further, a foam was prepared by the method of Example 1, and the foam density thereof was measured.

[ Comparative example 5]

Powder-shaped linear polypropylene homopolymer (Mn: 60,000 g/mol, Mw: 300,000 g/mol, Mz: 800,000 g/mol) 100 parts by weight and 3 parts by weight of diisopropyl peroxydicarbonate without prior stirring, Examples A pellet (branched polypropylene resin) was prepared in the same manner as in 1, and its melt extensibility (v120) and melt tension (F120) were measured. Further, a foam was prepared by the method of Example 1, and the foam density thereof was measured.

division Stirring conditions PP structure Melt extensibility (v120)
(mm/s) Melt tension (F120)
(cN) Foam density
(g/cm3) Example 1 80 ℃ Branched 236 31 0.32 Comparative Example 1 - Linear 156 3.0 0.71 Comparative Example 3 65 ℃ Branched 160 16 0.50 Comparative Example 4 120 ℃ Branched 130 5 0.79 Comparative Example 5 Agitation Branched 178 13 0.58

According to the results of Table 2, it can be seen that in Comparative Examples 3 to 5, the foaming density is lower than that of Example 1.

Specifically, in the case of Comparative Example 3 in which the stirring temperature is less than the range of the present invention, it can be confirmed that the melt extensibility (v120) and the melt tension (F120) are not sufficiently high. This is a result of insufficient premixing of linear polypropylene and organic peroxide due to an excessively low stirring temperature, and it can be seen that similar physical properties to Comparative Example 5 without prior mixing are exhibited.

In addition, in the case of Comparative Example 4 in which the stirring temperature exceeded the range of the present invention, it can be seen that a remarkably low melt tension (F120) appears. This is a result of excessive reaction during premixing due to an excessively high stirring temperature, resulting in a polymer chain breaking phenomenon.

Claims (5)

(a) In an inert atmosphere, a linear polypropylene resin having a melt index of 0.1 g/10min or more and 10.0 g/10min or less, measured according to ASTM D1238, and an organic peroxide having a half-life of 120°C of 1 second or less, at a temperature of 70°C or more and 110°C or less Stirring in; And
(b) following step (a), reacting at a temperature of 150° C. or more and 230° C. or less; and
In the step (b), the first antioxidant is added at the beginning of the reaction, and the second antioxidant is added at the time when the 10% to 95% reaction proceeds, a method for producing a branched polypropylene resin. The method according to claim 1,
The organic peroxide is a method for producing a branched polypropylene resin, characterized in that peroxydicarbonate. The method according to claim 1,
The content of the organic peroxide is 0.1 parts by weight or more and 5 parts by weight or less based on 100 parts by weight of the linear polypropylene resin. It is manufactured according to the manufacturing method of any one of claims 1 to 3, and the v120 melt extensibility measured according to ISO 16790:2005 is 200 mm/s or more and 250 mm/s or less, and the F120 melt tension is 20 cN or more and 35 cN or less. , Branched polypropylene resin. A foam comprising the branched polypropylene resin according to claim 4 and having a foam density of 0.4 g/cm 3 or less.

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