CN115891353A - A kind of straight line easy to tear, transparent synthetic paper and its preparation method and application - Google Patents

Abstract

The invention belongs to the technical field of synthetic paper, and discloses transparent synthetic paper easy to tear linearly, and a preparation method and application thereof. The synthetic paper comprises a heat sealing layer, a core layer and a corona layer from top to bottom, wherein the heat sealing layer, the core layer and the corona layer respectively comprise an easy-tearing master batch, and the easy-tearing master batch comprises dicyclopentadiene petroleum resin or carbon nonahydrogenation petroleum resin. According to the invention, by adding the easy-tearing master batch into each layer of the synthetic paper, the synthetic paper not only has easy-tearing performance (the tearing resistance is less than 2500 mN), but also has high transparency (the haze is less than 14%), high stiffness, easy tearing of the imitation paper and Zhang Tingxing effect.

Description

A straight-line, easy-to-tear, transparent synthetic paper and its preparation method and application

Technical Field

The present invention belongs to the technical field of synthetic paper, and in particular relates to a linear, easy-to-tear, transparent synthetic paper and a preparation method and application thereof.

Background Art

Paper made from plant fibers greatly facilitates people's writing, printing and information transmission. It is also a traditional packaging material and is widely used in daily life. However, paper is generally not water-resistant and opaque, and lacks in use and decorative effects. For this reason, people have developed a variety of imitation paper products, which greatly expand the application field, mainly made of plastic. The general synthetic paper production method is to add fillers and titanium dioxide to polypropylene resin, and after melt plasticization and biaxial stretching process, a BOPP film with good flatness and excellent printing performance is formed. Its water resistance and weather resistance are greatly improved, and it is widely used in newspapers, magazines, books, etc. to replace paper. However, BOPP film is difficult to tear or the tear is jagged, and BOPP film is opaque. In addition, there is a general polyolefin cast film, which has the advantages of good transparency, heat sealability, and small shrinkage, but due to the high tear resistance, it is difficult to tear during the use of packaging. When the film needs to be torn, the tearing force is too large, and there are filaments or jagged edges, causing the contents of the package to be thrown and lost, which greatly affects the efficiency of use. Therefore, in order to achieve the performance of traditional paper that is easy to tear in a straight line, improving the film's unidirectional straight-line tearing performance has always been an urgent need in the synthetic paper film industry. The current basic method is to stretch the film in a unidirectional or bidirectional manner to orient the molecular chains, thereby achieving the straight-line tearing function. In fact, after bidirectional stretching, the film has a certain inclination angle when it is torn. Although unidirectional stretching can tear in a straight line, the film's heat sealing property decreases, and defects such as easy shrinkage also follow.

Summary of the invention

The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a linear easy-to-tear, transparent synthetic paper and its preparation method and application. The synthetic paper of the present invention not only has the easy-to-tear property, but also has high transparency.

The first aspect of the present invention provides a synthetic paper, which includes a heat seal layer, a core layer and a corona layer from top to bottom, wherein the heat seal layer, the core layer and the corona layer all include an easy-tear masterbatch, and the easy-tear masterbatch includes dicyclopentadiene petroleum resin or carbon nine hydrogenated petroleum resin. Each layer is made of the easy-tear masterbatch, which can significantly improve the mechanical properties of the synthetic paper and reduce the tear resistance of the synthetic paper, thereby achieving a better easy-tear effect without affecting the transparency.

Preferably, the mass proportion of the easy-tear masterbatch in the heat-sealing layer, the core layer, and the corona layer is 10-30%. By limiting the amount of the easy-tear masterbatch, a more ideal easy-tear effect can be achieved; if the mass proportion of the easy-tear masterbatch is less than 10%, the tearing performance is poor; if the mass proportion of the easy-tear masterbatch is higher than 30%, such as 35%, it is easy to melt or break at the extruder die head and cannot form a normal film. When it reaches more than 40%, it cannot form a film at all.

Preferably, the synthetic paper has a thickness of 60-150 μm.

Preferably, the heat-sealing layer further comprises at least one of copolymer PP (polypropylene), LLDPE (linear low-density polyethylene), LDPE (low-density polyethylene), anti-adhesion masterbatch and slip masterbatch.

Preferably, the heat-sealing layer further comprises LLDPE, anti-adhesion masterbatch and slip masterbatch. The melting point of copolymerized PP, LLDPE or LDPE is relatively low, so that the synthetic paper has low-temperature heat-sealing performance; the anti-adhesion masterbatch can prevent the synthetic paper from sticking, making it easy to roll up and unroll, and easy to open; the slip masterbatch can reduce the friction coefficient of the synthetic paper surface, improve the slip opening performance, and improve the use performance of the synthetic paper.

Preferably, the mass proportion of the LLDPE in the heat-sealing layer is 66-86%.

Preferably, the anti-sticking masterbatch accounts for 1-5% by mass in the heat-sealing layer.

Preferably, the slip masterbatch accounts for 1-5% by mass in the heat-sealing layer.

Preferably, the heat-sealing layer has a thickness of 10-30 μm.

Preferably, the core layer further comprises at least one of homopolymer PP, MLLDPE (metallocene linear low-density polyethylene), and antistatic masterbatch.

Preferably, the core layer further comprises homopolymer PP or MLLDPE, and antistatic masterbatch. Homopolymer PP or MLLDPE as the main material of the core layer enables the synthetic paper to have good physical and mechanical properties, optical properties, etc. Homopolymer PP or MLLDPE has high hardness and stiffness, and combined with the modification of the easy-tear masterbatch, the stiffness is further improved, and it has the effect of easy tearing and stiffness of imitating paper; the antistatic masterbatch can reduce the surface resistivity of the synthetic paper, can prevent dust, and improve the unwinding performance and use performance of the synthetic paper.

Preferably, the mass proportion of the homopolymer PP or MLLDPE in the core layer is 66-87%.

Preferably, the antistatic masterbatch accounts for 1-5% by weight in the core layer.

Preferably, the core layer has a thickness of 30-100 μm.

Preferably, the corona layer further comprises at least one of copolymer PP, LLDPE, LDPE and anti-adhesion masterbatch.

Preferably, the corona layer further comprises copolymerized PP and an anti-blocking masterbatch.

Preferably, the copolymer PP accounts for 66-87% by mass in the corona layer.

Preferably, the anti-adhesion masterbatch accounts for 1-5% by mass in the corona layer.

Preferably, the thickness of the corona layer is 5-20 μm.

Preferably, the easy-tear masterbatch is selected from easy-tear masterbatch A or easy-tear masterbatch B.

Preferably, the easy-tear masterbatch A is prepared by the following preparation method:

The LLDPE carrier resin and the carbon nine hydrogenated petroleum resin are added into a high-speed mixer, stirred and mixed, and then melted and plasticized by a twin-screw extruder, dispersed and mixed, and then cooled, stretched and pelletized to obtain an easy-tear masterbatch A.

Preferably, the easy-tear masterbatch B is prepared by the following preparation method:

The LLDPE carrier resin and dicyclopentadiene petroleum resin are added into a high-speed mixer, stirred and mixed, and then melted and plasticized by a twin-screw extruder, dispersed and mixed, and then cooled, stretched and pelletized to obtain an easy-tear masterbatch B.

Preferably, the anti-adhesion masterbatch is prepared by the following preparation method:

The LLDPE carrier resin and the synthetic silica anti-blocking agent are added into a high-speed mixer, stirred and mixed, and then melted and plasticized by a twin-screw extruder, dispersed and mixed, and then cooled, stretched and pelletized to obtain an anti-blocking masterbatch.

Preferably, the slip masterbatch is prepared by the following preparation method:

The LLDPE carrier resin and the amide lubricant are added into a high-speed mixer, stirred and mixed, and then melted and plasticized by a twin-screw extruder, dispersed and mixed, and then cooled, stretched and pelletized to obtain a lubricant masterbatch.

Preferably, the antistatic masterbatch is prepared by the following preparation method:

The LLDPE carrier resin and the amine or lipid antistatic agent are added into a high-speed mixer, stirred and mixed, and then melted and plasticized by a twin-screw extruder, dispersed and mixed, and then cooled, stretched and pelletized to obtain an antistatic masterbatch.

Preferably, the stirring speed of the high-speed mixer is 100-300r/min, and the stirring time is 1-3min; the screw diameter of the twin-screw extruder is 30-80mm, the aspect ratio is 35-50, the temperature of the extruder is 180-230°C, the die temperature of the extruder is 200°C, the feeding speed is 10-60r/min, the screw speed is 100-300r/min, the supercooled water length is not more than 0.5m, and the speed of the pelletizer is 100-300r/min.

A second aspect of the present invention provides a method for preparing the synthetic paper of the present invention, comprising the following steps:

The raw materials of the heat seal layer, the core layer and the corona layer are melted respectively by different screw extruders, and then the melts are extruded through the die of a multi-channel co-extruder head;

The melt is cooled at 10-20°C to form a film, and then subjected to corona treatment to obtain the synthetic paper. It is understood that the cooling casting device used for cooling can be composed of a casting roller and a cooling water tank, or only a cooling casting roller, and is mainly used to quickly cool the melt coming out of the die head to form a film. The setting of the cooling temperature has a great influence on the transparency and heat shrinkage of the film.

Preferably, the temperature of the screw extruder and the die is 200-260° C. The screw extruder can be a single screw extruder or a twin screw extruder, and the temperature setting range of the extruder is 200-260° C. The reason is that if the temperature is too low, the resin is not well plasticized, resulting in poor film appearance, and even the melt is difficult to extrude; if the temperature is too high, the resin is easy to decompose, thereby affecting product performance and even production stability.

Preferably, the power of the corona treatment is 1-1.5 kvA. The corona treatment oxidizes the film surface with polar groups and achieves a slight roughening effect, increasing the surface tension of the polyolefin to more than 38 dynes, which is beneficial for subsequent application processes such as gluing, printing, and hot stamping.

A third aspect of the present invention provides use of the synthetic paper of the present invention in packaging materials.

Based on the above application, the present invention further provides a packaging bag, which is made of the synthetic paper described in the present invention.

Compared with the prior art, the beneficial effects of the present invention are as follows:

By adding easy-tear masterbatch to each layer of the synthetic paper of the present invention, the synthetic paper not only has easy-tear performance (tear resistance less than 2500mN), but also has high transparency (haze less than 14%) and high stiffness, and has the easy-tear and stiffness effects of imitating paper.

The preparation method of the synthetic paper of the present invention adopts a three-layer co-extrusion casting process for one-step forming, does not require unidirectional or bidirectional stretching of the film, is simple and easy to operate, has low cost, and is suitable for large-scale industrial production.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the effects of the synthetic paper of Example 1 and the synthetic paper of Comparative Example 1 after being torn.

DETAILED DESCRIPTION

In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

Unless otherwise specified, the raw materials, reagents and devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

In the following examples and comparative examples:

LLDPE uses Maoming Petrochemical Linear Polyethylene DFDA-7042;

Homopolymer PP uses Maoming Petrochemical Polypropylene Resin F300M;

MLLDPE uses Dow Chemical's medium-density polyethylene 2036P;

The ternary copolymer PP adopts Singapore TPC FS5612;

The carbon nine hydrogenated petroleum resin used is R1140 from Eastman Chemical Company;

Dicyclopentadiene petroleum resin uses OP501 from Nippon Petrochemical;

The lipid antistatic agent uses Evonik Degussa's glyceryl monostearate TEGIN PELLET;

The synthetic silica anti-adhesion agent used is AB750 from PQ Company of the United States, with an average particle size of 5μm;

The amide lubricant is erucamide E from Akzo Nobel Chemical Company, with a melting point of 85°C.

The easy-tear masterbatch A is prepared by the following preparation method:

50% by mass of LLDPE carrier resin and 50% by mass of carbon nine hydrogenated petroleum resin are added into a high-speed mixer, stirred and mixed, melted and plasticized by a twin-screw extruder, dispersed and mixed, and then cooled, stretched and pelletized to obtain an easy-tear masterbatch A.

The easy-tear masterbatch B is prepared by the following preparation method:

50% by mass of LLDPE carrier resin and 50% by mass of dicyclopentadiene petroleum resin are added into a high-speed mixer, stirred and mixed, melted and plasticized by a twin-screw extruder, dispersed and mixed, and then cooled, stretched and pelletized to obtain an easy-tear masterbatch B.

The anti-adhesion masterbatch is prepared by the following preparation method:

95% by mass of LLDPE carrier resin and 5% of synthetic silica anti-blocking agent are added into a high-speed mixer, stirred and mixed, melted and plasticized by a twin-screw extruder, dispersed and mixed, and then cooled, stretched and pelletized to obtain an anti-blocking masterbatch.

The slip masterbatch is prepared by the following preparation method:

90% by mass of LLDPE carrier resin and 10% by mass of amide lubricant are added into a high-speed mixer, stirred and mixed, melted and plasticized through a twin-screw extruder, dispersed and mixed, and then cooled, stretched and pelletized to obtain a lubricant masterbatch.

The antistatic masterbatch is prepared by the following preparation method:

The LLDPE carrier resin and lipid antistatic agent are added into a high-speed mixer, stirred and mixed, and then melted and plasticized by a twin-screw extruder, dispersed and mixed, and then cooled, stretched and pelletized to obtain an antistatic masterbatch.

The device parameters used in the preparation process of the above masterbatches are as follows: the stirring speed of the high-speed mixer is 200r/min, and the stirring time is 3min; the screw diameter of the twin-screw extruder is 50mm, the aspect ratio is 40, the temperature of the extruder is 200℃, the die temperature of the extruder is 200℃, the feeding speed is 40r/min, the screw speed is 200r/min, the supercooling water length is 0.3m, and the speed of the pelletizer is 200r/min.

Example 1

A synthetic paper comprises a heat sealing layer, a core layer and a corona layer from top to bottom. The raw materials and contents of each layer are shown in Table 1.

Table 1

The method for preparing the synthetic paper of this embodiment comprises the following steps:

The raw materials of the heat seal layer, the core layer and the corona layer are melted by different screw extruders respectively, and then the melt is extruded through the die of a multi-channel co-extruder head (T-die); the temperature of the screw extruder and the die is 200°C;

The melt is cooled by the casting roller to form a film, and then undergoes corona treatment, traction, and winding to obtain synthetic paper; the temperature of the casting roller is 20°C and the power of the corona treatment is 1.5kvA.

Example 2

A synthetic paper comprises a heat sealing layer, a core layer and a corona layer from top to bottom. The raw materials and contents of each layer are shown in Table 2.

Table 2

The preparation method of the synthetic paper in this embodiment is the same as that in Embodiment 1.

Example 3

A synthetic paper comprises a heat sealing layer, a core layer and a corona layer from top to bottom. The raw materials and contents of each layer are shown in Table 3.

Table 3

The preparation method of the synthetic paper in this embodiment is the same as that in Embodiment 1.

Example 4

The difference from Example 1 is that in Example 4, the easy-tear masterbatch A in the heat sealing layer, the core layer, and the corona layer are all replaced with the easy-tear masterbatch B, and the other raw materials, amounts, and preparation methods are the same as in Example 1.

Example 5

The difference from Example 2 is that in Example 5, the easy-tear masterbatch A in the heat sealing layer, core layer and corona layer is replaced by easy-tear masterbatch B, and other raw materials, amounts and preparation methods are the same as in Example 2.

Example 6

The difference from Example 3 is that in Example 6, the easy-tear masterbatch A in the heat sealing layer, core layer and corona layer is replaced by easy-tear masterbatch B, and other raw materials, amounts and preparation methods are the same as in Example 3.

Example 7

The difference from Example 1 is that in Example 7, the homopolymer PP of the core layer is replaced by MLLDPE, and other raw materials, amounts and preparation methods are the same as in Example 1.

Example 8

The difference from Example 2 is that in Example 8, the homopolymer PP of the core layer is replaced by MLLDPE, and other raw materials, amounts and preparation methods are the same as in Example 2.

Example 9

The difference from Example 3 is that in Example 9, the homopolymer PP of the core layer is replaced by MLLDPE, and other raw materials, amounts and preparation methods are the same as in Example 3.

Example 10

The difference from Example 1 is that in Example 10, the easy-tear masterbatch A in the heat sealing layer, core layer and corona layer is replaced by easy-tear masterbatch B, and the homopolymer PP of the core layer is replaced by MLLDPE. Other raw materials, amounts and preparation methods are the same as in Example 1.

Embodiment 11

The difference from Example 2 is that in Example 11, the easy-tear masterbatch A in the heat sealing layer, core layer and corona layer is replaced by easy-tear masterbatch B, and the homopolymer PP of the core layer is replaced by MLLDPE. Other raw materials, amounts and preparation methods are the same as in Example 2.

Example 12

The difference from Example 3 is that in Example 12, the easy-tear masterbatch A in the heat sealing layer, core layer and corona layer is replaced by easy-tear masterbatch B, and the homopolymer PP of the core layer is replaced by MLLDPE. Other raw materials, amounts and preparation methods are the same as in Example 3.

Comparative Example 1

A synthetic paper comprises a heat sealing layer, a core layer and a corona layer from top to bottom. The raw materials and contents of each layer are shown in Table 4.

Table 4

The preparation method of the synthetic paper in this comparative example is the same as that in Example 1.

Comparative Example 2

A synthetic paper comprises a heat sealing layer, a core layer and a corona layer from top to bottom. The raw materials and contents of each layer are shown in Table 5.

Table 5

The preparation method of the synthetic paper in this comparative example is the same as that in Example 1.

Comparative Example 3

The difference from Example 1 is that in the method for preparing synthetic paper of Comparative Example 3, the temperature of the casting roller is 30°C, and other preparation conditions, raw materials and amounts are the same as those in Example 1.

The synthetic papers prepared in Examples 1-12 and Comparative Examples 1-3 were subjected to performance tests, and the results are shown in Table 6.

Table 6

As can be seen from Table 6, Comparative Example 1 does not add the easy-tear masterbatch of the present invention, resulting in a tear resistance significantly greater than that of Example 1 and Example 4; Comparative Example 2 does not add the easy-tear masterbatch of the present invention, resulting in a tear resistance significantly greater than that of Example 7 and Example 10, the elastic modulus of Comparative Examples 1 and 2 is reduced (low stiffness), it is not easy to tear, and it is difficult to meet the requirements; After the modification of the easy-tear masterbatch in Examples 1-12, the tear resistance of the synthetic paper is greatly reduced, while the longitudinal and transverse tear resistance of general plastic films are all above 3000mN. When tearing by hand, people feel laborious, and the tear is not straight, and it is easy to produce jagged edges. Traditional paper is relatively easy to tear below 2500mN. The tear resistance of the synthetic paper provided by the present invention is also below 2500mN, and at the same time, the elastic modulus is increased (stiffness is improved), the transparency is increased, the heat shrinkage rate is low, the size is stable, the heat sealing strength is greater than 5N, and deep processing such as heat sealing, embossing, and printing can be performed, with the tear resistance and stiffness effects of imitating paper. The temperature of the casting roller in the preparation process of Comparative Example 3 is relatively high, resulting in a significant increase in haze and a decrease in transparency.

The synthetic paper of Example 1 was torn and compared with the synthetic paper of Comparative Example 1. The results are shown in FIG1 . It can be clearly seen that after the synthetic paper of Example 1 is torn by hand, the tear is straight and has no jagged edges; while after the synthetic paper of Comparative Example 1 is torn by hand, the tear is not straight and has obvious jagged edges.

The preferred embodiments of the present invention are specifically described above, but the invention is not limited to the embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims (10)

1. The synthetic paper is characterized by comprising a heat sealing layer, a core layer and a corona layer from top to bottom, wherein the heat sealing layer, the core layer and the corona layer respectively comprise an easily-torn master batch, and the easily-torn master batch comprises dicyclopentadiene petroleum resin or carbon nonahydrogenation petroleum resin.

2. The synthetic paper according to claim 1, wherein the easy-tear masterbatch comprises 10-30% of the heat-seal layer, the core layer and the corona layer.

3. The synthetic paper of claim 1, wherein the heat seal layer further comprises at least one of co-polypropylene, LLDPE, LDPE, anti-blocking masterbatch, and slip masterbatch.

4. The synthetic paper of claim 1, wherein the core layer further comprises at least one of homopolymeric PP, MLLDPE, antistatic masterbatch.

5. The synthetic paper of claim 1, wherein the corona layer further comprises at least one of co-polypropylene, LLDPE, LDPE, and anti-blocking masterbatch.

6. The method of making synthetic paper according to any of claims 1 to 5, comprising the steps of:

melting the raw materials of the heat-sealing layer, the core layer and the corona layer respectively through different screw extruders, and then extruding a melt through a die orifice of a multi-runner co-extruder head;

and cooling the melt at 10-20 ℃ to form a film, and performing corona treatment to obtain the synthetic paper.

7. The method of making synthetic paper according to claim 6, wherein the temperature of the screw extruder and the die is 200-260 ℃.

8. The method of making synthetic paper according to claim 6, wherein the corona treatment has a power of 1-1.5kvA.

9. Use of the synthetic paper according to any one of claims 1 to 5 in packaging materials.

10. A packaging bag, characterized by being made of the synthetic paper according to any one of claims 1 to 5.

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