阅读说明：本技术 阻光低密度收缩膜及其制备方法 (Light-blocking low-density shrink film and preparation method thereof ) 是由 冯益强 刘希军 李光耀 尹长奇 王凯 于 2020-06-09 设计创作，主要内容包括：本发明涉及一种阻光低密度收缩膜及其制备方法,属于热收缩聚酯薄膜技术领域。本发明所述的阻光低密度收缩膜,至少包括A层和B层,其中：A层为黑色阻光层,包括以下质量百分含量的原料：0.1-30％的黑色遮蔽剂,60-99.9％的改性聚对苯二甲酸乙二醇酯,0-30％的成孔剂；B层为白色遮蔽层,包括以下质量百分含量的原料：5-40％的白色遮蔽剂,40-95％的改性聚对苯二甲酸乙二醇酯,0-30％的成孔剂；A层和B层中的成孔剂不同时取0％。本发明所述的阻光低密度收缩膜,不仅具有优异的阻光效果,还具有较低的密度,成本低；同时本发明提供了一种简单易行的制备方法。(The invention relates to a light-blocking low-density shrink film and a preparation method thereof, belonging to the technical field of heat-shrinkable polyester films. The light-blocking low-density shrink film at least comprises an A layer and a B layer, wherein: the layer A is a black light-blocking layer and comprises the following raw materials in percentage by mass: 0.1-30% of black masking agent, 60-99.9% of modified polyethylene glycol terephthalate and 0-30% of pore-forming agent; the layer B is a white shielding layer and comprises the following raw materials in percentage by mass: 5-40% of white masking agent, 40-95% of modified polyethylene terephthalate and 0-30% of pore-forming agent; the pore-forming agent in the A layer and the B layer is not 0 percent at the same time. The light-blocking low-density shrink film has excellent light-blocking effect, lower density and low cost; meanwhile, the invention provides a simple and feasible preparation method.)

1. A light-blocking low-density shrink film characterized by: at least comprising an A layer and a B layer, wherein:

the layer A is a black light-blocking layer and comprises the following raw materials in percentage by mass:

0.1-30% of black masking agent, 60-99.9% of modified polyethylene glycol terephthalate and 0-30% of pore-forming agent;

the layer B is a white shielding layer and comprises the following raw materials in percentage by mass:

5-40% of white masking agent, 40-95% of modified polyethylene terephthalate and 0-30% of pore-forming agent;

the pore-forming agent in the A layer and the B layer is not 0 percent at the same time.

2. The light blocking low density shrink film of claim 1, wherein: modified polyethylene terephthalate, which is copolymerized with terephthalic acid and ethylene glycol by taking one or more of diol or diacid components with the molar mass content of 7-50% as a third monomer, wherein the total molar mass of all the monomers is taken as a reference.

3. The light blocking low density shrink film of claim 1, wherein: the black masking agent is inorganic dye, organic black pigment or organic black dye.

4. The light blocking low density shrink film of claim 1, wherein: the white masking agent is an inorganic colorant or incompatible organic microparticles.

5. The light blocking low density shrink film of claim 4, wherein: the inorganic colorant is one or more of titanium dioxide, calcium carbonate, barium sulfate, silicon dioxide, alumina or kaolin.

6. The light blocking low density shrink film of claim 1, wherein: the pore-forming agent is one or more of polyethylene, polypropylene, polystyrene, polycarbonate resin, polyacrylate resin, acrylic resin particles, melamine resin particles, silicone resin particles, crosslinked polystyrene particles, PMP, COC or cellulose acetate.

7. A method for preparing a light-blocking low-density shrink film according to any one of claims 1 to 6, characterized in that: respectively mixing the raw materials at least comprising the layer A and the layer B, then carrying out melt extrusion, carrying out ultra-cold sheet casting, and then sequentially carrying out longitudinal stretching, transverse stretching, corona treatment and traction rolling to obtain the light-blocking low-density shrink film.

8. The method of producing a light-blocking low-density shrink film according to claim 7, wherein: the melt extrusion temperature was 200-300 ℃.

9. The method of producing a light-blocking low-density shrink film according to claim 7, wherein: the stretching is performed 3 to 6 times in the main shrinkage direction, and the stretching is performed 1.0 to 1.5 times in the direction perpendicular to the main shrinkage direction.

10. The method of producing a light-blocking low-density shrink film according to claim 9, wherein: after stretching, heat treatment is carried out at 60-110 ℃.

Technical Field

The invention relates to a light-blocking low-density shrink film and a preparation method thereof, belonging to the technical field of heat-shrinkable polyester films.

Background

Polyester heat shrinkable film (PET heat shrinkable film for short) is a novel heat shrinkable packaging material, and the market demand is rapidly increased in recent years. Because the PET heat shrinkable film has the characteristics of high shrinkage, good transparency, no toxicity, no odor, good mechanical property, excellent printing performance, lower self shrinkage, relative storage resistance, environmental protection conformity and the like, the PET heat shrinkable film successfully replaces a polyvinyl chloride (PVC) heat shrinkable film in developed countries and becomes an ideal shrink packaging material.

In the use process of a common polyester shrink film, the common polyester shrink film is made of transparent materials, has small light barrier property and cannot protect a bottle body and substances sensitive to light in the bottle, and the bottle body is designed into a light-blocking material in the market at present, so that the bottle body is difficult to recycle due to the addition of a large amount of light-blocking agents.

Although the light blocking rate of white shrink films and ultraviolet-blocking shrink film products sold in the market at present can reach 80-90%, the products needing to be protected are still greatly damaged, and the requirement of the products on the quality guarantee period cannot be met. Thus, there is a need for more effective black light blockers.

After adding more effective black light-blocking agent, the surface layer needs to be covered with black due to the requirements of printing and surface beauty so as to present better advertising effect. However, the density of the light-blocking components is higher, and the density of the film is obviously increased after the light-blocking components are added, so that the using area of unit total amount is reduced, and the cost is greatly increased. The density of the transparent film of the PET shrink film was about 1.32g/cm³About, the density of the PET shrinkage film added with the masking agent reaches 1.4g/cm³Left and right.

Disclosure of Invention

The invention aims to provide a light-blocking low-density shrink film which not only has excellent light-blocking effect, but also has lower density and low cost; meanwhile, the invention provides a simple and feasible preparation method.

The light-blocking low-density shrink film at least comprises an A layer and a B layer, wherein:

the layer A is a black light-blocking layer and comprises the following raw materials in percentage by mass:

0.1-30% of black masking agent, 60-99.9% of modified polyethylene terephthalate glycol (PETG) and 0-30% of pore-forming agent;

the layer B is a white shielding layer of the layer A, and comprises the following raw materials in percentage by mass:

5-40% of white masking agent, 40-95% of modified polyethylene terephthalate and 0-30% of pore-forming agent;

the pore-forming agent in the A layer and the B layer is not 0 percent at the same time.

If necessary, C layer or more can be added, and C layer or more can be covered on the B layer as printing layer, and can also be covered on the A layer as white covering layer or transparent layer. The layer C is preferable and comprises the following raw materials in percentage by mass:

0-30% of pore-forming agent, 0-40% of white masking agent, 40-99% of modified polyethylene glycol terephthalate and 0-10% of opening slip agent.

In the preparation of the shrink film of the present invention, various additives such as an opening agent, a slip agent, an antistatic agent, an antioxidant, a nucleating agent, a tackifier, a viscosity reducer, a chain extender, a heat stabilizer, a hydrolysis resistant agent, a coloring pigment, an anti-coloring agent, an ultraviolet absorber, and the like may be added as needed.

The modified polyethylene terephthalate glycol (PETG) is prepared by copolymerizing one or more of common diol or diacid components with 7-50% (based on the total mass of all monomers) of molar mass content serving as a third monomer with terephthalic acid and ethylene glycol.

The third monomer diacid for modifying the polyethylene terephthalate can be phthalic acid, isophthalic acid, naphthalene dicarboxylic acid, adipic acid, azelaic acid, decanedicarboxylic acid sebacate, 1, 4-cyclohexanedicarboxylic acid and the like.

The third monomer glycol for modifying the polyethylene terephthalate can be 2, 2-dimethyl-1, 3-propanediol, 2-n-butanol-2-ethyl-1, 3-propanediol, 1, 4-butanediol, neopentyl glycol, hexanediol, 1, 4-cyclohexanedimethanol, ethylene glycol monobutyl ether and the like.

The above components can be copolymerized singly or in multiple ways, or blended after copolymerization.

The third monomer diol or diacid of the modified polyethylene terephthalate accounts for more than 7 percent and less than 50 percent of the total mole content of the diol or diacid, the shrinkage rate of the third monomer diol or diacid is not enough to obtain more than 40 percent of the shrinkage rate in 100 ℃ water bath for 10 seconds, and the strength of the film is reduced by more than 50 percent to influence the using effect. More preferably, it is 15% or more and 35% or less.

The black masking agent is inorganic dye such as carbon black and graphite, and can also be organic black pigment and organic black dye. The above materials may be used singly or in combination.

The black masking agent accounts for the total weight of the film, and the content of the black masking agent is less than 0.1 percent, so that the masking effect is poor; the shielding layer is required to be thick to achieve a good shielding effect, and the content of the shielding layer is more than 30%, the dispersion is difficult and the strength performance of the film is influenced, and more preferably more than 1% and less than 20%.

The white shielding agent is one or more inorganic coloring agents of titanium dioxide, calcium carbonate, barium sulfate, silicon dioxide, alumina, kaolin and the like, and also comprises incompatible organic particles, such as cycloolefin resin particles of polypropylene, PMP, COC and the like, cellulose triacetate resin particles and the like. The above masking agents may be used singly or in combination.

The pore-forming agent is one or more of polyethylene, polypropylene, polystyrene, polycarbonate resin, polyacrylate resin, acrylic resin particles, melamine resin particles, silicone resin particles, crosslinked polystyrene particles, PMP, COC and cellulose acetate.

At least one of the layer A and the layer B is added with a pore-forming agent, in order to obtain lower density, the addition amount is more than 5 percent and less than 30 percent of the weight ratio of the layer, less than 5 percent can not obtain effective pore-forming effect, and more than 30 percent affects film-forming property and shrinkage rate.

The layers a, B and C described in the present invention are merely referred to for distinguishing the number of layers, and are not limited to a specific layer.

The preparation method of the light-blocking low-density shrink film comprises the following steps:

(1) drying the raw materials corresponding to the layers A and B or the layers A, B and C respectively at 65 ℃ for 4 hours in dry air, extruding by using respective extruders, and if a vacuumizing double-screw extruder is used, drying is not needed. The extrusion temperature is 200-300 ℃;

(2) the melt extruded by each extruder enters a multilayer adapter through a respective filter metering pump and the like to form a mixture of a multilayer structure, and then flows out through a T-shaped die head to form the required sheet-shaped molten resin with the multilayer structure. Or preferably, a multilayer die head is used for converging and mixing at the position close to the outlet of the die head to form a multilayer co-extruded sheet-shaped outflow layer, so that the thickness uniformity of each layer can be maintained easily by the outflow layer, and the stability of the product quality is maintained;

(3) cooling the sheet-like outflow melt layer on a sheet casting roller at about 30 ℃ to form an unstretched sheet;

(4) performing single or bidirectional stretching at 10-50 deg.C higher than softening point, optionally longitudinal or transverse unidirectional stretching, optionally simultaneously longitudinal and transverse stretching, with no limitation on the sequence of transverse and longitudinal directions, or synchronous bidirectional stretching;

in this case, it is preferable to perform stretching in the longitudinal direction by 1.0 to 1.5 times and stretching in the transverse direction by 3 to 6 times, in order to achieve relatively high productivity in the transverse direction, and to suitably improve the longitudinal tensile strength in the longitudinal direction, which is advantageous for the stability of the subsequent processing and use processes. After stretching, heat treatment can be carried out at 60-110 ℃;

(5) after longitudinal stretching, one or two surfaces of the film can be subjected to coating treatment, and the coating can be a smooth coating, an antistatic coating, an antibacterial coating and the like and is used for improving the adhesive force;

(6) coiling the film into a large roll after trimming, or carrying out corona treatment before coiling;

(7) and cutting into the specifications required by the customers and packaging.

The light-blocking low-density shrink film prepared by the invention meets the following conditions:

a, transmittance of less than 1%, more preferably less than 0.5%, and further preferably less than 0.1%.

b, the shrinkage in the main shrinkage direction of the water bath at 100 ℃ for 10 seconds is more than 40 percent, and more preferably more than 50 percent.

And c, the shrinkage rate in the direction perpendicular to the main shrinkage direction in a water bath for 10 seconds at 100 ℃ is less than 10%.

d, the thickness of the A layer is more than 10 microns, and the A layer is used as a white shielding layer of the printing layer to the black layer.

And e, adding a pore-forming agent into at least one layer of the layer A or the layer B, wherein the addition amount is more than 5 percent of the total weight of the film.

The light-blocking low-density shrink film prepared by the invention successfully maintains the required shrinkage rate, has excellent light shielding property, greatly reduces the density of the product, reduces the cost and simultaneously obtains excellent surface attractiveness. The density of the product of the invention is lower than 1.3g/cm³More preferably less than 1.2g/cm³Further preferably less than 1.1g/cm³。

When the density is reduced to a sufficiently small extent, e.g. less than 1.0g/cm³The method can be used for separating the bottle labels in water in the bottle recycling process.

When the surface layer (printing layer) of the C layer only contains the pore-forming agent and no other shielding agent, the C layer presents a special pearlescent effect, and the attractiveness and the advertising effect of the product are improved.

Compared with the prior art, the invention has the following beneficial effects:

(1) according to the invention, a certain proportion of black masking agent is added into the layer A, so that the product has excellent light resistance;

(2) in order to realize that the black color of the layer A does not influence the printing effect, a white shielding agent with a certain proportion is added into the layer B, so that the black layer is shielded, and the printing effect and the attractiveness are good;

(3) in the invention, the pore-forming agent is added into at least one of the layer A and the layer B, thereby greatly reducing the density of the product and lowering the actual use cost of customers;

(4) when the printing surface only contains the pore-forming agent and does not contain other white masking agents, the film produced by the invention has special pearlescent effect;

(5) the preparation method of the light-blocking low-density shrink film is simple and feasible and is beneficial to industrial production.

Detailed Description

The present invention will be described in detail below with reference to specific examples, but the present invention is not limited to these examples.