CN112659690A - High-transparency high-gloss heat shrinkable film and preparation method thereof - Google Patents

Abstract

The invention provides a high-transmittance high-gloss heat shrinkable film and a preparation method thereof, which can solve the technical problem that the definition and the gloss of the conventional heat shrinkable film need to be further improved. A high-transmittance high-gloss heat shrinkable film is 25-75 mu m in thickness and is formed by co-extruding an outer layer, a middle layer and an inner layer through film blowing; the method is characterized in that: the outer layer comprises mLLPE and HDPE, the middle layer comprises HDPE, mLLPE and LDPE, and the inner layer comprises mLLPE and HDPE; in the whole heat shrinkable film, the mLLPE is 45-65%, the LDPE is 10-25%, and the HDPE is 20-30%. Tests show that the haze and the glossiness of the high-transmittance high-gloss heat shrinkable film are greatly superior to those of the conventional similar products.

Description

High-transparency high-gloss heat shrinkable film and preparation method thereof

Technical Field

A high-transparency high-gloss heat shrinkable film and a preparation method thereof belong to the technical field of high polymer materials, further belong to the field of novel high polymer functional film materials, and particularly belong to the technical field of packaging films.

Background

With the rapid development of Chinese economy and the improvement of the quality of life of people, the requirement on environmental protection is higher and higher in future, and some low-quality shrink films which influence human body safety are eliminated rapidly, so that the shrink films are replaced more safely and more environmentally. With the continuous change of market demands, the heat shrinkable film is developing towards multi-layer and functional directions, and a plurality of new technologies and new requirements (such as shrinkage rate, high transparency, high gloss, high strength, thinning and cost reduction, low-temperature heat sealing and the like) appear.

The High-Transparency High-Gloss heat shrinkable Film (SFPE-HTG) has excellent performance, and has the advantages of High tensile breaking strength, relatively low average density, High shrinkage and difficult aging. The heat shrinkable film can shrink quickly at low temperature, has good sealing performance at high speed, and can obtain ideal skin packaging effect after thinning. The shrink package of the heat shrinkable film not only has exquisite appearance, but also plays a role in moisture prevention, dust prevention, loosening prevention and burglary prevention. The heat shrinkable film integrates the advantages of high efficiency, energy conservation, remarkable cost saving, light weight, waste reduction, higher identification degree, brand improvement and the like, and gradually becomes the mainstream of the heat shrinkable film market.

In the same industry, when the thickness of the existing high-transmittance high-gloss heat shrinkable film is 75 micrometers, the haze is about 18%, the gloss is about 62%, the product wrapped inside is blurred visually, and when the thickness is 30 micrometers, the haze is also reduced to about 9%, and the visual definition of the product is improved. However, different customers have different requirements on the thickness of the high-transmittance high-gloss heat-shrinkable film, and the requirement of customers on only reducing the thickness of the film to improve the definition and the gloss of the film obviously cannot be met.

Disclosure of Invention

The invention provides a high-transmittance high-gloss heat shrinkable film and a preparation method thereof, which can solve the technical problem that the definition and the gloss of the conventional high-transmittance high-gloss heat shrinkable film need to be further improved.

The technical scheme is that the high-transmittance high-gloss heat shrinkable film is 25-75 μm thick and is formed by bonding an outer layer, a middle layer and an inner layer; the method is characterized in that:

the raw materials of the outer layer comprise mLLPE (metallocene) and HDPE (high density polyethylene), the raw materials of the middle layer comprise HDPE, mLLPE and LDPE (low density polyethylene), and the raw materials of the inner layer comprise mLLPE and HDPE;

in the whole heat shrinkable film, the mLLPE is 45-65%, the LDPE is 10-25%, and the HDPE is 20-30%.

Further, the outer layer comprises 90% mLLPE and 10% HDPE by mass percent;

the middle layer comprises 40% of HDPE, 40% of mLLPE and 20% of LDPE according to mass percentage;

the inner layer comprises 90% of mLLPE and 10% of HDPE in percentage by mass;

the melt index MI of the mPE and the HDPE is 1, the melt index MI of the MPE is 0.25, and the melt index MI of the LDPE is 0.33.

Further, the thickness ratio of the outer layer, the middle layer and the inner layer is 1: 2: 1.

further, the mLLPE is Exxon Mobil 1018MA, the HDPE is samsung-dadao Da F920, the middle mLLPE is Exxon Mobil 4002MC, and the LDPE is Shenhua 2420D.

The invention also provides a preparation method of the high-transmittance high-gloss heat shrinkable film, which is characterized by comprising the following steps: comprises the following steps of (a) carrying out,

(1) weighing raw materials of different varieties according to the weight ratio and uniformly mixing;

(2) the raw materials of the outer layer, the middle layer and the inner layer respectively enter three central feeding screw type extruders to be extruded and discharged,

wherein, the raw materials of the inner layer and the outer layer enter an extruder with the temperature of 210 ℃, are heated and plasticized, and are extruded into a die cavity through the rotation of a screw rod, the raw material of the middle layer enters the extruder with the temperature of 225 ℃, and are heated and plasticized, and are extruded into the die cavity through the rotation of the screw rod;

(3) the outer layer, the middle layer and the inner layer are automatically bonded into a whole in a die cavity with the die temperature of 220 ℃ and enter a die opening gap, the automatically bonded hot material is blown into a film bubble by compressed air, automatic circulating cooling is carried out by an inner air channel and an outer air channel, the film bubble adjusts the thickness of the film by longitudinal traction, adjusts the width of the film by transverse blowing, and the film bubble is shaped by a herringbone plate to prepare the heat shrinkable packaging film.

According to the high-transmittance high-gloss heat shrinkable film disclosed by the invention, through tests, the thickness ratio of the outer layer to the middle layer to the inner layer is 1: 2: in the case of 1, the number of the cells,

when the whole film thickness is 75 μm, the haze is 9.2% and the gloss (45 °) is 76%; when the whole film thickness is 30 μm, the haze is 5.2% and the gloss (45 °) is 90.5%; the high-transmittance high-gloss heat shrinkable film disclosed by the invention is greatly superior to the existing similar products in haze and glossiness.

Detailed Description

Example 1

A high-transmittance high-gloss heat shrinkable film is 75 μm thick and is composed of three layers of coextruded and bonded films, namely an outer layer, a middle layer and an inner layer, wherein the thickness ratio of the outer layer to the middle layer to the inner layer is 1: 2: 1;

the outer layer comprises 90% mLLPE and 10% HDPE, the middle layer comprises 40% HDPE, 40% mLLPE and 20% LDPE, and the inner layer comprises 90% mLLPE and 10% HDPE;

the outer and inner mLLPE have the same weight, a melt index MI of 1, a density of 0.918 g/cm, and are obtained by thin film epitaxy from Exxon Mobil 1018 MA;

the outer layer, the middle layer and the inner layer are the same, have a melt index MI of 1 and a density of 0.96 g/cm, are obtained by carrying out thin film bearing and high-density thin film bearing on a thin film bearing part, and are selected from samsung-dadadahr F920;

the middle layer mLLPE has a melt index MI of 0.25 and a density of 0.94 g/cm, and is selected from Exxon Mobil 4002 MC;

LDPE has a melt index MI of 0.33 and a density of 0.923 g/cm, and is obtained by ethanol chromatography at 2420D.

The preparation method of the high-transmittance high-gloss heat shrinkable film comprises the following steps,

(1) weighing raw materials of different varieties according to the weight ratio and uniformly mixing;

(2) the raw materials of the outer layer, the middle layer and the inner layer respectively enter three central feeding screw type extruders to be extruded and discharged,

wherein, the raw materials of the inner layer and the outer layer enter an extruder with the temperature of 210 ℃, are heated and plasticized, and are extruded into a die cavity through the rotation of a screw rod, the raw material of the middle layer enters the extruder with the temperature of 225 ℃, and are heated and plasticized, and are extruded into the die cavity through the rotation of the screw rod;

(3) the outer layer, the middle layer and the inner layer are automatically bonded into a whole in a die cavity with the die temperature of 220 ℃ and enter a die opening gap, the automatically bonded hot material is blown into a film bubble by compressed air, automatic circulating cooling is carried out by an inner air channel and an outer air channel, the film bubble adjusts the thickness of the film by longitudinal traction, adjusts the width of the film by transverse blowing, and the film bubble is shaped by a herringbone plate to prepare the heat shrinkable packaging film.

The heat shrinkable film obtained in this example had a haze of 9.2%, a gloss (45 ℃) of 76%, a tensile strength at break (TD/MD) of 32.2/27.1MPa, an elongation (TD/MD) of 682/780%, and a shrinkage (130 ℃ C.. times.20 seconds, MD/TD) of 72/22%. Compared with the existing similar products, the haze is 18%, the glossiness is 62%, the haze is reduced by 48.9%, and the glossiness is improved by 22.6%.

Example 2

Example 2 unlike example 1, example 2 produced a high-transmittance high-gloss heat shrinkable film having a thickness of 30 μm.

The heat shrinkable film obtained in this example had a haze of 5.2%, a gloss (45 °) of 90.5%, a tensile strength at break (MD/TD) of 42/37MPa, an elongation at break (MD/TD) of 1200/1520%, and a heat shrinkage (130 ℃ x 20 seconds, MD/TD) of 77/24%. The haze was reduced by 53.3% compared to a heat shrinkable film of equivalent thickness in the applicant's prior application publication No. CN 107244121B.

Claims (5)

1. A high-transmittance high-gloss heat shrinkable film is 25-75 mu m in thickness and is formed by co-extruding an outer layer, a middle layer and an inner layer through film blowing; the method is characterized in that:

the outer layer is made of mLLPE and HDPE, the middle layer is made of HDPE, mLLPE and LDPE, and the inner layer is made of mLLPE and HDPE;

in the whole heat shrinkable film, the mLLPE is 45-65%, the LDPE is 10-25%, and the HDPE is 20-30%.

2. The high-transmittance high-gloss heat-shrinkable film according to claim 1, wherein: the outer layer comprises 90% of mLLPE and 10% of HDPE in percentage by mass;

the middle layer comprises 40% of HDPE, 40% of mLLPE and 20% of LDPE according to mass percentage;

the inner layer comprises 90% of mLLPE and 10% of HDPE in percentage by mass;

the melt index MI of the mLLPE and the HDPE is 1, the melt index MI of the middle mLLPE is 0.25, and the melt index MI of the LDPE is 0.33.

3. The high-transmittance high-gloss heat-shrinkable film according to claim 2, wherein: the thickness ratio of the outer layer to the middle layer to the inner layer is 1: 2: 1.

4. the high-transmittance high-gloss heat-shrinkable film according to claim 2, wherein: the mLLPE is Exxon Mobil 1018MA, the HDPE is Samsung-Dadall F920, the middle mLLPE is Exxon Mobil 4002MC, and the LDPE is Shenhua 2420D.

5. The method for preparing a high-transmittance high-gloss heat-shrinkable film according to any one of claims 1 to 4, wherein: the method comprises the following steps:

(1) weighing raw materials of different varieties according to the weight ratio and uniformly mixing;

(2) the raw materials of the outer layer, the middle layer and the inner layer respectively enter three central feeding screw type extruders to be extruded and discharged,

wherein, the raw materials of the inner layer and the outer layer enter an extruder with the temperature of 210 ℃, are heated and plasticized, and are extruded into a die cavity through the rotation of a screw rod, the raw material of the middle layer enters the extruder with the temperature of 225 ℃, and are heated and plasticized, and are extruded into the die cavity through the rotation of the screw rod;

(3) the outer layer, the middle layer and the inner layer are automatically bonded into a whole in a die cavity with the die temperature of 220 ℃ and enter a die opening gap, the automatically bonded hot material is blown into a film bubble by compressed air, automatic circulating cooling is carried out by an inner air channel and an outer air channel, the film bubble adjusts the thickness of the film by longitudinal traction, adjusts the width of the film by transverse blowing, and the film bubble is shaped by a herringbone plate to prepare the heat shrinkable packaging film.