Polypropylene resin composition for casting film core layer, preparation method and casting polypropylene film

Abstract

The invention provides a polypropylene resin composition for a core layer of a cast film, a preparation method of the polypropylene resin composition and a cast polypropylene film. The polypropylene resin composition comprises polypropylene resin and an inorganic nanoparticle auxiliary agent with the particle size of 100 nm or below. The polypropylene resin composition provided by the invention has improved mechanical properties, and can give consideration to both high transparency and anti-blocking and anti-opening properties, and a film prepared from the polypropylene resin composition has low haze and good anti-blocking property.

Description

Technical Field

[0001] The invention belongs to the field of synthetic resin preparation, and particularly relates to a polypropylene resin composition for a cast film core layer, a preparation method and a cast polypropylene film. Background Art

[0002] CPP film is cast polypropylene film, also known as unstretched polypropylene film. It can be divided into general CPP film, aluminized grade CPP film and cooking grade CPP film according to different uses. Strictly speaking, mainly due to the nature of the process, CPP film usually has a certain orientation only in the longitudinal direction. Rapid cooling on the cold casting roller gives the film excellent clarity and finish. The main characteristics of CPP film include: lower cost and higher output compared with other films such as LLDPE, LDPE, HDPE, PET, PVG; higher stiffness than PE film; excellent water vapor and odor barrier; multifunctional, can be used as a composite material base film; can be metallized; when used for food and commodity packaging, it has excellent demonstration, and the product is still clearly visible under the packaging.

[0003] Since CPP film is very thin and easy to stick, a certain amount of anti-sticking agent should be added during production to prevent the product quality from being affected by sticking to the roller. It is difficult to take into account both high transparency and anti-sticking opening performance when using traditional opening agents in the production of CPP film. The main reason is that high transparency and easy opening performance are a pair of contradictions in traditional technology. Traditional opening agents are mostly inorganic micron materials with a particle size of several microns. When the amount added is small, the effect on haze is small but the anti-sticking effect is poor. When the amount added is large, the anti-sticking effect is good but the effect on haze is large and the mechanical properties of the film will be reduced. Summary of the invention

[0004] In view of this, the purpose of the present invention is to address the defects in the prior art and provide a polypropylene resin composition for a cast film core layer, a preparation method and a cast polypropylene film. The polypropylene resin composition of the present invention has improved mechanical properties, can take into account both high transparency and anti-blocking opening performance, and the film made thereof has lower haze and good anti-blocking performance.

[0005] The objectives of the present invention are achieved through the following technical solutions.

[0006] In a first aspect, the present invention provides a polypropylene resin composition for a core layer of a cast film, wherein the polypropylene resin composition comprises a polypropylene resin and an inorganic nanoparticle auxiliary agent having a particle size of less than 100 nm.

[0007] The present inventor has found that, by adding the inorganic nanoparticle auxiliary agent with particle diameter below 100nm in polypropylene resin, the polypropylene resin composition that obtains can take into account high transparency performance and anti-adhesion opening performance, and the film made by it has low mistiness and good anti-adhesion performance. It is believed that adopting the inorganic nanoparticle auxiliary agent with particle diameter below 100nm to come modified polypropylene resin can play the effect of strengthening and toughening, and simultaneously because the particle diameter of the inorganic nanoparticle auxiliary agent is below 100nm, lower than the wavelength (500-700nm) of visible light, can not influence the transparency and the transmittance of the polypropylene resin composition film. In addition, the inorganic nanoparticle auxiliary agent also has the nucleation function, is evenly dispersed into the polymer matrix (polypropylene resin) and also can have the improvement effect to the mechanical property, the optical property of polymer.

[0008] According to the present invention, the polypropylene resin composition has a melt flow rate of 7 to 9 g / 10 min at 190° C. and 2.16 kg as measured according to ASTM D1238.

[0009] According to the polypropylene resin composition provided by the present invention, the polypropylene resin has ethylene repeating units and propylene repeating units. In some embodiments, the content of ethylene repeating units in the polypropylene resin is 1 to 5 mol%, preferably 3.6 to 4.0 mol%. It is believed that in the polypropylene resin, as the content of ethylene repeating units increases, the crystallinity of the polypropylene resin decreases, the melting point decreases, and the impact performance of the product improves. The reduction in melting point is conducive to reducing the heat sealing temperature and widening the heat sealing temperature range. This will be beneficial to downstream packaging processing and save costs.

[0010] According to the polypropylene resin composition provided by the present invention, the polypropylene resin is prepared by a method comprising the following steps: in the presence of a main catalyst, using propylene as a monomer and ethylene as a comonomer to carry out a polymerization reaction.

[0011] In some embodiments, the conditions of the method for preparing the polypropylene resin include: a reaction temperature of 70±2.5°C, a reaction pressure of 3.4-3.8 MPa, and a hydrogen concentration of 500-1500 ppm; and / or the main catalyst is a DOQ-C catalyst, for example, a DQC-401 catalyst, and triethylaluminum is used as a co-catalyst; and / or DONOR-C is used as an electron donor; and / or Atmer163 is used as an antistatic agent.

[0012] In some preferred embodiments, the amount of ethylene used is 1 to 5 mol%, preferably 3.6 to 4.0 mol%, based on the total amount of propylene and ethylene.

[0013] In the present invention, there is no particular limitation on the amount of the main catalyst, the co-catalyst, the electron donor and the antistatic agent, and the conventional amounts in the art may be used.

[0014] In some preferred embodiments, the amount of the main catalyst used can be 30-50 kg / ton of polypropylene resin. For example, the amount of catalyst DQC-401 used is 40 kg / ton of polypropylene resin.

[0015] In some preferred embodiments, the molar ratio of the co-catalyst to propylene is 0.14 to 0.22:1, for example 0.16:1.

[0016] In some preferred embodiments, the molar ratio of the co-catalyst to the electron donor is 6 to 16:1, preferably 8 to 12:1, for example 10:1.

[0017] In some preferred embodiments, the amount of the antistatic agent used is 2-3 kg / ton of polypropylene resin.

[0018] According to the polypropylene resin composition provided by the present invention, the particle size of the inorganic nanoparticle auxiliary agent is 1 to 100 nm, preferably 10 to 100 nm, more preferably 20 to 80 nm, and most preferably 50 to 80 nm.

[0019] According to the polypropylene resin composition provided by the present invention, the inorganic nanoparticle auxiliary agent may include barium sulfate nanoparticles and an optional color adjuster, and the refractive index is preferably 1.49 to 1.50. Such a refractive index is similar to that of the polypropylene resin, and after the inorganic nanoparticle auxiliary agent is added to the polypropylene resin, the haze of the film will not increase.

[0020] In some embodiments, the barium sulfate nanoparticles may be spherical. It is believed that spherical inorganic nanoparticles aid in dispersion.

[0021] In some embodiments, the barium sulfate nanoparticles may be unsurface-treated or surface-treated, and are preferably surface-treated nano-barium sulfate.

[0022] In some preferred embodiments, the surface-treated nano-barium sulfate is nano-barium sulfate surface-treated with silane coupling agent KH-570. The surface-treated barium sulfate nanoparticles can be homemade or commercially available.

[0023] In some specific embodiments, the surface-treated barium sulfate nanoparticles are prepared by a method comprising the following steps:

[0024] S1. Dispersing silane coupling agent KH-570 in water or ethanol to obtain a treatment solution;

[0025] S2. Adding unsurface-treated barium sulfate nanoparticles into a treatment solution at 50-80° C. with stirring to treat the barium sulfate nanoparticles, and filtering and drying the treated barium sulfate nanoparticles to obtain the surface-treated barium sulfate nanoparticles.

[0026] In step S1, the content of the silane coupling agent KH-570 in the treatment liquid is 0.1 to 2% by weight, preferably 0.5 to 0.6% by weight.

[0027] In some embodiments, the color adjuster is nano titanium dioxide.

[0028] In some embodiments, the weight ratio of the barium sulfate nanoparticles to the color adjuster in the inorganic nanoparticle additive is 1 to 3:1, preferably 1.5 to 2.5:1.

[0029] According to the polypropylene resin composition provided by the present invention, the amount of the inorganic nanoparticle auxiliary agent is 0.15-0.3 wt %, preferably 0.18-0.22 wt %, and more preferably 0.19-0.22 wt %, based on the weight of the polypropylene resin composition.

[0030] According to the polypropylene resin composition provided by the present invention, the polypropylene resin composition further comprises an antioxidant and / or a halogen absorber.

[0031] In some embodiments, the antioxidant includes a primary antioxidant and a secondary antioxidant.

[0032] In the present invention, the primary antioxidant may be a phenolic antioxidant. Examples of phenolic antioxidants suitable for use in the present invention include, but are not limited to, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and n-octadecylβ-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate. When used, the primary antioxidant is used in an amount of 0.1 to 0.2% by weight based on the weight of the polypropylene resin composition.

[0033] In the present invention, the auxiliary antioxidant may be a phosphite antioxidant. Examples of phosphite antioxidants suitable for use in the present invention include, but are not limited to, bis(2,4-di-tert-butylphenol)pentaerythritol diphosphite and tris[2,4-di-tert-butylphenyl]phosphite. When used, the auxiliary antioxidant is used in an amount of 0.05 to 0.1% by weight based on the weight of the polypropylene resin composition.

[0034] In some preferred embodiments, the weight ratio of the primary antioxidant to the auxiliary antioxidant is 1 to 3:1, preferably 1.5 to 2.5:1, for example, 2:1.

[0035] In some embodiments, the halogen absorbent is calcium stearate and / or zinc stearate. When used, the amount of the halogen absorbent is 0.03 to 0.1% by weight based on the weight of the polypropylene resin composition.

[0036] According to the polypropylene resin composition provided by the present invention, wherein, based on the weight of the polypropylene resin composition, the polypropylene resin composition comprises:

[0037]

[0038] In a second aspect, the present invention provides a method for preparing a polypropylene resin composition, wherein the preparation method comprises: mixing, extruding and granulating a polypropylene resin, an inorganic nanoparticle auxiliary agent, an optional antioxidant and an optional halogen absorber.

[0039] According to the preparation method provided by the present invention, the mixing is carried out at normal temperature and pressure, and the mixing time is preferably 2 to 6 minutes.

[0040] In the present invention, the extrusion is carried out by a twin-screw extruder, and the extrusion temperature is preferably 166-230°C.

[0041] According to the preparation method provided by the present invention, the polypropylene resin is prepared by a method comprising the following steps: in a loop reactor, in the presence of a main catalyst, polymerization reaction is carried out using propylene as a monomer and ethylene as a comonomer.

[0042] In some embodiments, the amount of ethylene used is 1 to 5 mol%, based on the total amount of propylene and ethylene.

[0043] In some embodiments, in the method for preparing polypropylene resin, the reaction conditions include: the reaction temperature is 70±2.5°C, the reaction pressure is 3.4-3.8 MPa, and the hydrogen concentration is 500-1500 ppm; and / or the main catalyst is a DOQ-C catalyst, for example, a DQC-401 catalyst, and triethylaluminum is used as a co-catalyst; and / or DONOR-C is used as an electron donor; and / or, Atmer163 is used as an antistatic agent.

[0044] In the present invention, the amounts of the main catalyst, the co-catalyst, the electron donor and the antistatic agent are as defined above.

[0045] In a third aspect, the present invention provides a cast polypropylene film, wherein the cast polypropylene film comprises a core layer formed of a polypropylene resin composition, a heat sealing layer and a corona layer.

[0046] According to the cast polypropylene film provided by the present invention, wherein, the present invention has no special requirements to heat seal layer and corona layer, and the composition of the heat seal layer and corona layer can be the same or different from the composition of the core layer. In some embodiments, the composition of the heat seal layer can be different from the composition of the core layer with the corona layer, for example, heat seal layer resin material and corona layer resin material as known in the art can be adopted.

[0047] Compared with the prior art, the present invention has the following advantages:

[0048] The polypropylene resin composition of the present invention has improved mechanical properties, and compared with conventional inorganic anti-adhesive additives, can take into account both high transparency and anti-adhesion opening properties, and the film made thereof has lower haze and good anti-adhesion properties. In particular, the tensile strength of the polypropylene resin composition of the present invention is ≥24MPa, the yellow index is <-3, the film haze is <3%, and the film adhesion is <30N / mm, and is particularly suitable for the core layer of a three-layer co-extruded polypropylene cast film. DETAILED DESCRIPTION

[0049] The present invention will be further described below in conjunction with specific embodiments, but they do not constitute any limitation to the present invention.

[0050] Preparation Example 1

[0051] The raw materials used to produce the polypropylene powder are shown in Table 1, and the main catalyst is DQC-401, and the co-catalysts are triethylaluminum (TEAL), DONOR-C and Atmer163.

[0052] Table 1 Main technical requirements for raw materials

[0053]

[0054] Propylene and ethylene are added to a loop reactor, and a main catalyst DQC-401, a cocatalyst triethylaluminum (TEAL), an electron donor DONOR-C and an antistatic agent Atmer163 are added, wherein the catalyst DQC-401 is added according to an output of 40 kg / ton of polypropylene resin; TEAL / C3 (propylene) = 0.16; TEAL / DONOR = 10; and the antistatic agent Atmer163 is 2.5 kg / ton of polypropylene resin. Stir evenly, control the reaction temperature in the loop reactor to 70±1°C, the reaction pressure to 3.6 MPa, the hydrogen concentration to 1000 ppm, and the bonded ethylene content to 3.6 mol%, to obtain a polypropylene powder.

[0055] The melt flow rate of the obtained polypropylene powder was 8 g / 10 min at 190° C. and 2.16 kg as measured according to ASTM D1238.

[0056] Preparation Example 2

[0057] 1. Preparation of surface-treated barium sulfate nanoparticles

[0058] (1) The silane coupling agent KH-570 was dispersed in anhydrous ethanol to obtain a treatment solution with a concentration of 0.6 wt %.

[0059] (2) Under stirring conditions at 60° C., unsurface-treated barium sulfate nanoparticles with a particle size of 50 to 70 nm are added to the treatment solution, stirred for 60 minutes, filtered and dried at 80° C. to obtain surface-treated barium sulfate nanoparticles.

[0060] 2. The surface-treated barium sulfate nanoparticles are mixed with nano-titanium dioxide having a particle size of 60 to 80 nm in a weight ratio of 4:1 to obtain an anti-sticky spherical inorganic nanoparticle additive.

[0061] Examples 1 to 5 Polypropylene resin composition for cast film core layer

[0062] According to the formula in Table 2, the polypropylene powder, antioxidant, inorganic nano-additive and halogen absorber of Preparation Example 1 were added into a mixer and mixed at room temperature and pressure for 5 minutes. Then, a twin-screw extruder was used for extrusion granulation. The temperature was controlled at 166-230°C and the temperature at the die head was 210°C to obtain a polypropylene resin composition for a cast film core layer.

[0063] Comparative Example 1

[0064] A polypropylene resin composition was prepared by using a method substantially the same as that of Example 1 according to the formula in Table 2. Specifically, in Comparative Example 1, barium sulfate having a particle size of 2 microns was used instead of the spherical inorganic nanoparticle auxiliary agent.

[0065] Comparative Example 2

[0066] A polypropylene resin composition was prepared by using a method substantially the same as that of Example 1 according to the formula in Table 2. Specifically, in Comparative Example 1, barium sulfate having a particle size of 200 nanometers was used instead of the anti-sticking spherical inorganic nanoparticle additive.

[0067] Table 2 Formulation of polypropylene resin composition of Examples 1 to 5 and Comparative Examples 1-2 Unit: weight %

[0068]

[0069] Properties of polypropylene resin compositions

[0070] In the present invention, the following test standards and methods are used to measure the properties of the polypropylene resin composition. The results are shown in Table 3.

[0071] Melt index: measured according to ASTM D1238, conditions: 190° C., 2.16 kg; unit: g / 10 min.

[0072] Yellowness index: measured according to GB / T2409-1980.

[0073] Ash content: measured according to GB / T9345-2008, unit: %.

[0074] Tensile strength: measured according to GB / T1040-2006, unit, MPa.

[0075] Flexural modulus: measured according to GB / T9341-2000, unit: GPa.

[0076] Izod impact strength: measured according to GB / T1843-2000, unit KJ / m 2 .

[0077] Table 3 Properties of polypropylene resin compositions of Examples 1 to 5 and Comparative Examples 1 to 2

[0078]

[0079] Polypropylene resin composition cast film

[0080] The polypropylene resin composition was subjected to a single-layer casting test using a three-layer co-extrusion cast film test machine produced by Swedish Labtech Engineering Ltd. The casting temperature was 230° C. and the speed was 190 m / min. The polypropylene resin cast film was cooled by a cold roller and then pulled and wound up.

[0081] The thickness of the cast film of the polypropylene resin composition was measured, the haze of the cast film of the polypropylene resin composition was measured according to GB / T2410-2008, the gloss was measured according to ASTM D2457, and the adhesion was measured according to GB / T16276-1996. The results are shown in Table 4.

[0082] Table 4 Properties of polypropylene resin composition cast film

[0083]

[0084]

[0085] It can be seen from Table 3 and Table 4 that the polypropylene resin composition of the present invention has improved mechanical properties, can take into account both high transparency and anti-blocking opening performance, and the film made therefrom has lower haze and good anti-blocking performance.

[0086] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A polypropylene resin composition for a cast film core layer, wherein: The polypropylene resin composition comprises polypropylene resin and inorganic nanoparticle auxiliary agent with a particle size of less than 100 nm.

2. The polypropylene resin composition according to claim 1, characterized in that The polypropylene resin has a melt flow rate of 7 to 9 g / 10 min at 190° C. and 2.16 kg as measured according to ASTM D1238; and / or The polypropylene resin has ethylene repeating units and propylene repeating units, and the content of the ethylene repeating units is 1 to 5 mol%, preferably 3.6 to 4.0 mol%.

3. The polypropylene resin composition according to claim 1 or 2, characterized in that: The polypropylene resin is prepared by a method comprising the following steps: in the presence of a main catalyst, using propylene as a monomer and ethylene as a comonomer to carry out a polymerization reaction; Preferably, the conditions of the method for preparing the polypropylene resin include: a reaction temperature of 70±2.5°C, a reaction pressure of 3.4-3.8MPa, and a hydrogen concentration of 500-1500ppm; and / or the main catalyst is a DOQ-C catalyst, for example, a DQC-401 catalyst, and triethylaluminum is used as a co-catalyst; and / or DONOR-C is used as an electron donor; and / or Atmer163 is used as an antistatic agent; More preferably, based on the total amount of propylene and ethylene, the amount of ethylene is 1 to 5 mol%, preferably 3.6 to 4.0 mol%; and / or, the amount of the main catalyst is 30 to 50 kg / ton of polypropylene resin; and / or, the molar ratio of the co-catalyst to propylene is 0.14 to 0.22:1; and / or, the molar ratio of the co-catalyst to the electron donor is 6 to 16:1; and / or, the amount of the antistatic agent is 2 to 3 kg / ton of polypropylene resin.

4. The polypropylene resin composition according to any one of claims 1 to 3, characterized in that The particle size of the inorganic nanoparticle auxiliary agent is 1 to 100 nm, preferably 10 to 100 nm, more preferably 20 to 80 nm, and most preferably 50 to 80 nm; and / or, The inorganic nanoparticle auxiliary agent includes barium sulfate nanoparticles and an optional color adjuster; Preferably, the barium sulfate nanoparticles are surface-treated nano-barium sulfate, preferably nano-barium sulfate surface-treated with silane coupling agent KH-570; Preferably, the color adjuster is nano titanium dioxide; Preferably, the weight ratio of the barium sulfate nanoparticles to the color adjuster in the inorganic nanoparticle additive is 1 to 3:1, preferably 1.5 to 2.5:

1.

5. The polypropylene resin composition according to any one of claims 1 to 4, characterized in that Based on the weight of the polypropylene resin composition, the amount of the inorganic nanoparticle additive is 0.15 to 0.3 weight %, preferably 0.18 to 0.22 weight %, and more preferably 0.19 to 0.22 weight %.

6. The polypropylene resin composition according to any one of claims 1 to 5, characterized in that The polypropylene resin composition further comprises a halogen absorber and / or an antioxidant; Preferably, the halogen absorber is calcium stearate and / or zinc stearate; Preferably, the amount of the halogen absorber is 0.03 to 0.1 wt % based on the weight of the polypropylene resin composition.

7. The polypropylene resin composition according to claim 6, characterized in that The antioxidants include primary antioxidants and auxiliary antioxidants; Preferably, the primary antioxidant is a phenolic antioxidant, preferably pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and / or β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; Preferably, the auxiliary antioxidant is a phosphite antioxidant, preferably bis(2,4-di-tert-butylphenol)pentaerythritol diphosphite and / or tris[2,4-di-tert-butylphenyl]phosphite; Preferably, based on the weight of the polypropylene resin composition, the amount of the primary antioxidant is 0.1-0.2 weight%, the amount of the auxiliary antioxidant is 0.05-0.1 weight%, and the weight ratio of the primary antioxidant to the auxiliary antioxidant is preferably 1-3:1, more preferably 1.5-2.5:1, for example, 2:

1.

8. The polypropylene resin composition according to any one of claims 1 to 7, characterized in that Based on the weight of the polypropylene resin composition, the polypropylene resin composition comprises: Polypropylene resin 99.4-99.6% by weight Main antioxidant 0.1~0.2 wt%, Auxiliary antioxidant 0.05~0.1 wt%, Halogen absorbent 0.03~0.1wt%, Inorganic nanoparticle additive 0.15-0.3% by weight.

9. The method for preparing the polypropylene resin composition according to any one of claims 1 to 8, wherein: The preparation method comprises: mixing, extruding and granulating polypropylene resin, inorganic nanoparticle auxiliary agent, optional antioxidant and optional halogen absorbent; Preferably, the mixing is carried out at normal temperature and pressure, and the mixing time is preferably 2 to 6 minutes; Preferably, the extrusion is carried out by a twin-screw extruder, and the extrusion temperature is preferably 166 to 230°C; Preferably, the polypropylene resin is prepared by a method comprising the following steps: carrying out a polymerization reaction in a loop reactor in the presence of a primary catalyst using propylene as a monomer and ethylene as a comonomer; More preferably, the reaction conditions in the method for preparing polypropylene resin include: a reaction temperature of 70±2.5°C, a reaction pressure of 3.4-3.8 MPa, and a hydrogen concentration of 500-1500 ppm; and / or the main catalyst is a DOQ-C catalyst, for example, a DQC-401 catalyst, and triethylaluminum is used as a co-catalyst; and / or DONOR-C is used as an electron donor; and / or Atmer163 is used as an antistatic agent.

10. A cast polypropylene film, wherein The cast polypropylene film comprises a core layer, a heat sealing layer and a corona layer formed by the polypropylene resin composition according to any one of claims 1 to 7 or the polypropylene resin composition obtained by the preparation method according to claim 8 or 9.

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