Polypropylene resin composition for heat sealing layer of cast film, preparation method and cast polypropylene film

Abstract

The invention provides a polypropylene resin composition for a heat sealing layer of a cast film, a preparation method and a cast polypropylene film, the polypropylene resin composition comprises polypropylene resin and an inorganic nanoparticle auxiliary agent, the inorganic nanoparticle auxiliary agent comprises barium sulfate nanoparticles, an amide slipping agent and an optional color adjusting agent, and the particle sizes of the nano barium sulfate and the color adjusting agent are respectively and independently less than 100nm. The polypropylene resin composition provided by the invention has improved mechanical properties and can give consideration to both high transparency and adhesion and opening resistance, and a film prepared from the polypropylene resin composition has relatively low haze and low friction coefficient.

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 heat-sealing layer, a preparation method and a cast polypropylene film. Background Art

[0002] CPP film is cast polypropylene film, also known as unstretched polypropylene film. CPP film has excellent heat resistance, acid resistance, alkali resistance, grease resistance, food contact safety, excellent appearance and packaging display performance, and can be used in hot filling, cooking bags, aseptic packaging and other fields, with broad market prospects. However, the price of cooking CPP is relatively high, and the supply is unstable. CPP film is very thin and easy to stick. In order to prevent the film from sticking, the film surface has a certain degree of roughness, a certain amount of air is maintained between the films, and the friction coefficient of the film is reduced. A certain modifier is added to the resin to become an anti-sticking agent; in order to improve certain properties of the film, it is often necessary to add a certain amount of additives to the resin. Therefore, it is a development trend to develop special materials for CPP films with high transparency, good heat sealing performance and anti-sticking.

[0003] It is difficult for traditional opening agents to take into account both high transparency and anti-adhesion opening performance. The main reason is that in traditional technology, high transparency and easy opening performance are a pair of contradictions: good transparency but poor opening performance; good opening performance but poor transparency. Traditional inorganic opening agents are mostly micron materials with a particle size of several microns. When added in a small amount, the effect on haze is small, but the anti-adhesion effect is poor. When added in a large amount, the anti-adhesion effect is good, but the effect on haze is large and the mechanical properties of the film will be reduced. Traditional lubricants are amide compounds, which have the advantage of fast onset, but their migration will affect the long-term use effect and the addition amount should not be too large. If it is too large, adhesion will occur easily, the lubrication function will be lost, and the transparency will be affected. 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 heat seal 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-sticking opening performance, and the film made thereof has lower haze and friction coefficient.

[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 cast film heat seal layer, wherein the polypropylene resin composition comprises a polypropylene resin and an inorganic nanoparticle auxiliary agent, the inorganic nanoparticle auxiliary agent comprises barium sulfate nanoparticles, an amide lubricant and an optional color adjuster, and the particle sizes of the nano barium sulfate and the color adjuster are each independently below 100 nm.

[0007] The present inventor has found that, by adding the inorganic nanoparticle auxiliary agent (nano barium sulfate and optional color and luster adjusting 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 low friction coefficient. 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 affect the transparency and the transmittance of polypropylene resin composition film. In addition, the inorganic nanoparticle auxiliary agent also has nucleation function, is evenly dispersed into the polymer matrix (polypropylene resin) and also can have 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, using triethylaluminum as a co-catalyst; and / or DONOR-C 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 can 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, 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 sizes of the nano-barium sulfate and the color adjuster are independently 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 additive comprises nano barium sulfate, an amide lubricant and an optional color adjuster, and its refractive index is generally 1.49 to 1.50. Such a refractive index is similar to that of polypropylene resin, and after the inorganic nanoparticle additive is added to the polypropylene resin, the haze of the film will not increase.

[0020] According to the polypropylene resin composition provided by the present invention, the nano barium sulfate may be spherical. It is believed that spherical inorganic nanoparticle additives are conducive to dispersion.

[0021] According to the polypropylene resin composition provided by the present invention, the amide lubricant is a fatty acid amide lubricant. Examples of fatty acid amide lubricants suitable for use in the present invention include, but are not limited to, erucamide and oleamide.

[0022] In some embodiments, the amide lubricant is a fatty acid amide composite lubricant, including erucamide and oleamide in a weight ratio of 3:1 to 1:3, for example, 3:1 to 1:1.

[0023] According to the polypropylene resin composition provided by the present invention, the color adjuster is nano titanium dioxide.

[0024] According to the polypropylene resin composition provided by the present invention, the weight ratio of nano barium sulfate, amide lubricant and color adjuster in the inorganic nano particle auxiliary agent is 1:0.4-0.6:0.1-0.5.

[0025] According to the polypropylene resin composition provided by the present invention, the amount of the inorganic nanoparticle auxiliary agent is 0.15 to 0.4 weight %, preferably 0.15 to 0.35 weight %, based on the weight of the polypropylene resin composition.

[0026] According to the polypropylene resin composition provided by the present invention, the polypropylene resin composition further comprises an antioxidant and / or a halogen absorber.

[0027] In some embodiments, the antioxidant includes a primary antioxidant and a secondary antioxidant.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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:

[0033]

[0034] 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.

[0035] 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.

[0036] In the present invention, the extrusion is carried out by a twin-screw extruder, and the extrusion temperature is preferably 166-230°C.

[0037] 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.

[0038] In some embodiments, the amount of ethylene used is 1 to 5 mol%, based on the total amount of propylene and ethylene.

[0039] In some embodiments, in the method for preparing polypropylene resin, the reaction conditions are as follows: 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; 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.

[0040] In the present invention, the amounts of the main catalyst, the co-catalyst, the electron donor and the antistatic agent are as defined above.

[0041] Compared with the prior art, the present invention has the following advantages:

[0042] The polypropylene resin composition of the present invention has improved mechanical properties. Compared with conventional inorganic anti-adhesive additives, it can take into account both high transparency and anti-adhesion opening properties. The film made from the polypropylene resin composition has lower haze and low friction coefficient. In particular, the tensile strength of the polypropylene resin composition of the present invention is ≥28MPa, the yellow index is <-3, the film haze is <3%, and the film adhesion is <30N / mm. It is particularly suitable for the heat sealing layer of a three-layer co-extruded polypropylene cast film. DETAILED DESCRIPTION

[0043] The present invention will be further described below in conjunction with specific embodiments, but they do not constitute any limitation to the present invention.

[0044] Preparation Example 1

[0045] 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.

[0046] Table 1 Main technical requirements for raw materials

[0047]

[0048] 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.

[0049] 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.

[0050] Preparation Example 2

[0051] The nano-barium sulfate, amide lubricant and color adjuster in a weight ratio of 1:0.5:0.25 are ball-milled to obtain a spherical inorganic nanoparticle additive, wherein the nano-barium sulfate has a particle size of 80 nm, the amide lubricant is erucic acid amide and oleic acid amide in a weight ratio of 2:1, and the color adjuster is nano-titanium dioxide with a particle size of 75 nm.

[0052] Examples 1 to 5 Polypropylene resin composition for cast film heat seal layer

[0053] According to the formula in Table 2, the polypropylene powder of Preparation Example 1, antioxidant, anti-stick spherical inorganic nano-additive and halogen absorber 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 mold was 210°C to obtain a polypropylene resin composition for a cast film heat sealing layer.

[0054] Comparative Example 1

[0055] 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 10 microns was used instead of the spherical inorganic nanoparticle auxiliary agent.

[0056] Comparative Example 2

[0057] A polypropylene resin composition was prepared by using a method substantially the same as that of Example 1 according to the formulation in Table 2. Specifically, in Comparative Example 2, barium sulfate with a particle size of 200 nm was used instead of the spherical inorganic nanoparticle auxiliary agent.

[0058] Table 2 Formulation of polypropylene resin compositions of Examples 1 to 5 and Comparative Examples 1 to 2 Unit: weight %

[0059]

[0060] Properties of polypropylene resin compositions

[0061] 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.

[0062] Melt index: measured according to ASTM D1238, conditions: 190° C., 2.16 kg; unit: g / 10 min.

[0063] Yellowness index: measured according to GB / T2409-1980.

[0064] Ash content: measured according to GB / T9345-2008, unit: %.

[0065] Tensile strength: measured according to GB / T1040-2006, unit, MPa.

[0066] Flexural modulus: measured according to GB / T9341-2000, unit: GPa.

[0067] Izod impact strength: measured according to GB / T1843-2000, unit KJ / m 2 .

[0068] Table 3 Properties of polypropylene resin compositions of Examples 1 to 5 and Comparative Examples 1 to 2

[0069]

[0070]

[0071] Polypropylene resin composition cast film

[0072] 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.

[0073] The thickness of the polypropylene resin composition cast film was measured, the haze of the polypropylene resin composition cast film was measured according to GB / T2410-2008, the gloss was measured according to ASTM D2457, the adhesion was measured according to GB / T16276-1996, and the friction coefficient was measured according to GB / T10006-1988. The results are shown in Table 4.

[0074] Table 4 Properties of polypropylene resin composition cast film

[0075]

[0076] 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-sticking opening performance, and the film made therefrom has lower haze and low friction coefficient.

[0077] 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 heat seal layer, wherein: The polypropylene resin composition comprises polypropylene resin and inorganic nanoparticle additives, wherein the inorganic nanoparticle additives comprise nano barium sulfate, an amide lubricant and an optional color adjuster, and the particle sizes of the nano barium sulfate and the color adjuster are independently below 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 sizes of the nano-barium sulfate and the color adjuster are independently 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 color adjuster is nano titanium dioxide; and / or, The amide lubricant is selected from at least one of erucamide and oleamide, preferably in a weight ratio of 3:1 to 1:3, for example, erucamide and oleamide in a ratio of 3:1 to 1:1; and / or, The weight ratio of nano barium sulfate, amide lubricant and color adjuster in the inorganic nano particle auxiliary agent is 1:0.4-0.6:0.1-0.

5.

5. The polypropylene resin composition according to any one of claims 1 to 4, characterized in that The amount of the inorganic nanoparticle additive is 0.15 to 0.4% by weight, preferably 0.15 to 0.35% by weight, based on the weight of the polypropylene resin composition.

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 0.15-0.35 wt%.

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; 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 and two heat-sealing layers formed from 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, wherein the heat-sealing layers are located outside the core layer.

Images