TWI658075B - Lightweight, low-shrink white polyester film - Google Patents

Abstract

The present invention is a lightweight, low-shrink white polyester film with a specific gravity in the range of 0.6 to 1.2 and including a three-layer structure of A / B / A. It is characterized in that the interior of layers A and B contains holes, wherein the layer A contains : 65 ~ 95wt% polyester resin and 5 ~ 35wt% inorganic particles. Layer B contains: 50 ~ 90wt% polyester resin, 5 ~ 25wt% modified polypropylene resin and 5 ~ 25wt% inorganic particles. The modified polypropylene resin is modified by using 0.1 ~ 3 phr peroxide as the cross-linking modification, the heat distortion temperature is above 120 ° C, and the melt index (MI) (temperature 230 ° C, load 2.16kg) is 0.2 ~ 1g / 10 minutes .

Description

Lightweight, low-shrink white polyester film

The invention relates to a polyester film with holes, excellent whiteness and low shrinkage. It has the characteristics of light specific gravity, tear resistance, good printability, shading, durability, economy and environmental protection, etc., and is applied to labels, stickers, posters, etc. , Recording paper or packaging materials.

Compared with natural paper, synthetic paper has higher strength, folding resistance, higher whiteness, good water resistance, no damage after immersion in water, and good printing performance. Therefore, it is mostly used in water-resistant newspapers, Books, maps, calendars, cards, labels, stickers, posters, and more.

The main raw materials of synthetic paper are polyethylene, polypropylene, polystyrene, polyester and other organic resins. Among them, polyester is widely used because it has properties such as excellent heat resistance and mechanical strength, and can develop various primers to increase the adhesion in accordance with customer ink requirements.

The method of forming voids in the polyester film is to add incompatible materials. After biaxial extension, bubbles will be generated along the incompatible material, resulting in a decrease in the specific gravity of the polyester film. The micropores scatter light and make the polyester film white.

For the purpose of weight reduction, in the prior art, for example, Japanese Patent No. 6-269995, as incompatible materials, polyolefin resins and polystyrene resins are preferred. Among them, polypropylene and polystyrene resins have cost advantages. However, due to the poor heat resistance of polypropylene and polystyrene resins, the lightening effect is not good and the longitudinal shrinkage is too high. Laser printing is easy to warp, which is not conducive to printing production.

Polymethylpentene (TPX) and polyolefin foaming patent (COC) have been successively proposed to improve the insufficient heat resistance and effectively achieve lightweight characteristics and increase reflectance. However, due to the expensive materials, the required manufacturing costs are relatively high. Can be used on reflective sheets, but not for synthetic paper applications.

The problem to be solved by the present invention is to provide a lightweight, low-shrinkage white film with a specific gravity of 0.6 to 1.2, a longitudinal shrinkage of less than 1%, and good dimensional stability, and is widely used in printing inks and laser printing.

In the present invention, by using specific modified polypropylene resin with inorganic particles, and controlling the particle size of the modified polypropylene during longitudinal stretching, the modified polypropylene can be prevented from deforming during stretching and heat fixing, thereby achieving light weight and low shrinkage. White polyester film and less prone to warp when applied to laser printing.

The present invention is a lightweight, low-shrink white polyester film, which includes an A / B / A three-layer structure, and is characterized in that the A layer contains (relative to the total combined amount of the A layer): 65 to 95% by weight of polyester resin and 5 to It is composed of 35wt% inorganic particles, and layer B contains (relative to the total combined amount of layer B): 50 ~ 90wt% polyester resin, 5 ~ 25wt% modified polypropylene resin and 5 ~ 25wt% inorganic particles; The thickness (total thickness of the two outermost layers) is 2% to 30% of the thickness of the entire polyester film;

The above modified polypropylene resin should be made in advance and meet the following conditions: (1) Adding 0.1 ~ 3wt% peroxide crosslinking modifier to polypropylene resin, (2) The heat distortion temperature needs to be 120 Above ℃, (3) Melt index (MI) is 0.2 ~ 1g / 10min under temperature 230 ℃, load 2.16kg, and specific gravity ranges from 0.6 to 1.2

A lightweight, low-shrinkage white polyester film according to the present invention includes at least a three-layer structure of A / B / A, which is characterized in that the inside of each of the layers A and B contains holes, wherein the layer A contains: 65 to 95 wt% Polyester resin and 5 ~ 35wt% inorganic particles, layer B contains: 50 ~ 90wt% polyester resin, 5 ~ 25wt% modified polypropylene resin and 5 ~ 25wt% inorganic particles, among which modified polypropylene resin The following conditions should be met: (1) 0.1 to 3 wt% peroxide is used as a cross-linking modifier relative to polypropylene, (2) the heat distortion temperature must be above 120 ° C, and (3) the melt index (MI) is The temperature is 230 ° C, the load is 0.2 to 1 g / 10 minutes under a load of 2.16 kg, and the specific gravity ranges from 0.6 to 1.2.

The polyester of layers A and B of the lightweight and low-shrinkage white polyester film of the present invention may be a homopolyester or a copolyester. Polyester refers to a product obtained by the condensation polymerization reaction of a diol and a dicarboxylic acid. In the obtained polymer, the diol is one or more alcohols of ethylene glycol, trimethylene glycol, tetramethylene glycol, cyclohexanedimethanol, diethylene glycol, and neopentyl glycol; the dicarboxylic acid is p-benzene One or more acids of dicarboxylic acid, isophthalic acid, phthalic acid, adipic acid, sebacic acid, and naphthalenedicarboxylic acid. The diol and the dicarboxylic acid may be used singly or in combination of two or more kinds. In the present invention, polyethylene terephthalate or polyethylene naphthalate is particularly preferred.

The lightweight, low-shrinkage white polyester film of the present invention contains inorganic particles in layer A. The inorganic particles may be selected from the group consisting of silica, barium sulfate, calcium carbonate, titanium dioxide, kaolin, talc, zeolite, alumina, zinc sulfide, and the like Above, the average particle diameter (D ₅₀ ) of the inorganic particles is 0.05-5 micrometers, but it is preferably 0.1-2 micrometers, and more preferably 0.2-1 micrometers. Among them, from the viewpoints of weight reduction and low shrinkage, barium sulfate, calcium carbonate, and titanium dioxide are preferred. The inorganic particles can be used alone, or two or more of them can be used in combination. The inorganic particles can be added to the polyester resin in advance, mixed uniformly, and made into a master batch to improve uniformity.

Relative to the total combined amount of layer A, the addition amount of inorganic particles in layer A is preferably 5 to 35 wt%. If it is less than 5 wt%, the holes cannot be pulled out and the weight reduction effect is not significant. When it is more than 35 wt%, there are too many surface holes As a result, the film is easily broken and a complete film cannot be formed.

A lightweight, low-shrinkage white polyester film of the present invention achieves lightweight characteristics by containing voids in the film. The formation of voids is achieved by uniformly and finely dispersing the polyester and the non-compatible resin, and by extending (for example, biaxial extension). Upon stretching, voids (air bubbles) are formed around the incompatible resin.

The B-layer non-compatible resin uses a specific modified polypropylene-based resin. The thermal deformation temperature of the modified polypropylene-based resin must be greater than 120 ° C. If the thermal deformation is lower than 120 ° C, the modified polypropylene is easily deformed and difficult to form in the extension section. Empty.

The modified polypropylene-based resin is a propylene homopolymer or a copolymer of propylene and one or more other α-olefins. The polypropylene (PP) of the present invention may be selected from the group consisting of homopolypropylene (PP-H), block copolymer polypropylene (PP-B), and random copolymer polypropylene (PP-R). Among them, polypropylene has a melt index (MI) usually within the range of 0.5 to 15 g / 10 minutes, preferably 1 to 10 g / 10 minutes, and most preferably 3 to 8 g / 10 minutes.

Modified polypropylene is modified with a peroxide cross-linking agent. When heated to the peroxide decomposition temperature during the process, the peroxide begins to decompose, the cross-linking agent starts to interact with the polypropylene resin to generate free radicals, and then cross-links to form a network. Structure, and greatly improve the physical properties such as heat resistance and tensile properties of polypropylene resin products.

The cross-linking agents used in the present invention are the following compounds [the number in parentheses is the decomposition temperature (in ° C)]: succinic acid peroxide (110 ° C), benzoyl peroxide (110 ° C), 2-ethylhexan Acid third butyl peroxide (113 ° C), p-chlorobenzidine peroxide (115 ° C), third butyl peroxyisobutyrate (115 ° C), third butyl peroxy isopropyl carbonate (135 ℃), tert-butyl perlaurate (140 ℃), 2,5-dimethyl-2,5-bis (peroxybenzylidene) hexane (140 ° C), tertiary butyl peroxyacetate (140 ° C), peroxodiphthalic acid di-third Butyl ester (140 ° C), maleic acid-third butyl ester (140 ° C), cyclohexanone peroxide (145 ° C), peroxybenzoic acid-third butyl ester (145 ° C), peroxidation Dicumyl (150 ° C), 2,5-dimethyl-2,5-bis (third-butyl-peroxy) hexane (155 ° C), third-butyl hydrogen peroxide (158 ° C) ), Di-third butyl peroxide (160 ° C), 2,5-dimethyl-2,5-bis (third-butylperoxy) hexyne (170 ° C), and α, α'- Bis-tertiary-butylperoxy-1,4-diisopropylbenzene (160 ° C). To select α, α'-bis-tertiary-butylperoxy-1,4-diisopropylbenzene and 2,5-dimethyl-2,5-di (tertiary-butylperoxy) hexane The alkyne is better because it has a higher decomposition temperature and is easy to control the physical properties and appearance quality stability of the modified polypropylene. The addition amount is preferably 0.1 to 3% by weight and more preferably 0.3 to 1.5% by weight relative to polypropylene. .

The cross-linking auxiliary is used as a cross-linking auxiliary for peroxide cross-linking or radical reaction cross-linking to improve the degree of cross-linking, including diolefins, triolefins, and tetraolefin compounds having two terminal carbon-carbon double bonds. The present invention is selected from: 1,9-decadiene, 1,7-octadiene, 1,5-hexadiene, 1,4-pentadiene, 1,3-butadiene, 1,3,5 -One or more auxiliary agents such as hexatriene, 2,3-dimethyl-1,3-butadiene, and the crosslinking auxiliary agent used in the present invention is trimethylolpropane triacrylate.

Polypropylene and peroxide are mixed and melted, and modified polypropylene pellets are produced by a single-screw extruder or a twin-screw extruder. Among them, the twin-screw extruder has a better mixing and dispersing effect. When melting and extruding, other resins or rubbers can be added as needed.

The modified polypropylene-based resin used in the present invention preferably has a melt index (MI) of 0.2 to 1 g / 10 minutes. When the MI is higher than 1 g / 10 minutes, deformation of the polypropylene-based dispersed particles is likely to occur, and it is difficult to form voids. When the MI is less than 0.1 g / 10 minutes, the dispersibility of the polypropylene-based dispersed particles is deteriorated, and although large voids can be formed to achieve lightweight characteristics, it is easy to form The size is not uniform, and the uniform shielding property cannot be obtained, and the film forming property is deteriorated.

The melt index (MI) is a measurement value based on ISO1133 under conditions of 230 ° C and a load of 2.16 kg.

The modified polypropylene resin is preferably added in an amount of 5 to 25% by weight, and more preferably 8 to 15% by weight, relative to the total combined amount of layer B. When the content of the modified polypropylene-based resin is less than 5 wt%, sufficient pores cannot be formed to achieve lightweight characteristics. On the other hand, when the content of the modified polypropylene-based resin exceeds 25% by weight, the film forming property tends to be deteriorated, which is not preferable.

Modified polypropylene can be mixed and dispersed with polyester first, or it can be added directly during film making. It is better to mix and disperse with polyester first, which helps to stabilize the dispersion of modified polypropylene in polyester. It also helps to uniform the formation of voids when the film is stretched, to achieve good shielding, lightweight characteristics, and low Shrinkage and production stability.

The lightweight, low-shrinkage white polyester film B layer of the present invention needs to contain inorganic particles, and is mainly used to assist the modified polypropylene and improve the heat resistance, so that the modified polypropylene is not easy to deform after being stretched, and the voids are easy to maintain, achieving a good light weight. Quantitative characteristics. Examples of inorganic particles include, but are not particularly limited to, silicon oxide, barium sulfate, calcium carbonate, titanium dioxide, kaolin, talc, zeolite, alumina, and zinc sulfide. In. Among them, from the viewpoint of weight reduction, barium sulfate, calcium carbonate, and titanium dioxide are preferred. The inorganic particles may be used singly or in combination of two or more kinds. Inorganic particles can be added to polyester resin or modified polypropylene resin in advance. Among them, it is better to add to modified polypropylene resin, which helps to further improve the heat resistance of modified polypropylene, and the lightweight effect after extension. Better.

The amount of inorganic particles added in the B layer is preferably 5 to 25% by weight relative to the total combined amount of the B layer. If it is less than 5wt%, it cannot effectively help the modified polypropylene to pull out the holes, resulting in insignificant weight reduction and insufficient shielding. When it is more than 25% by weight, the mechanical strength is insufficient due to too many surface voids. The average particle diameter (D ₅₀ ) of the inorganic particles is 0.05-5 micrometers, but it is preferably 0.1-2 micrometers, and more preferably 0.2-1 micrometers.

The lightweight and low-shrink white polyester film of the present invention has a three-layer structure of A / B / A, in which the thickness of the A layer (the total thickness of the two outermost layers) relative to the thickness of the entire film is preferably 2 % To 30%, more preferably 5% to 15%. When the thickness of the A layer is less than 2%, the film is broken due to the large inner layer voids and the dimensional stability is not good. On the other hand, when the thickness of the A layer is more than 30%, it is difficult to have a lightweight property.

The lightweight and low-shrinkage white polyester film of the present invention may contain other additives in addition to those described above. Examples of the other additives include antioxidants, heat stabilizers, matting agents, pigments, ultraviolet absorbers, fluorescent whitening agents, plasticizers, and other additives. In particular, in order to suppress oxidative degradation of the modified polypropylene-based resin, it is preferable to contain an antioxidant or a heat stabilizer.

The lightweight and low-shrink white polyester film of this product can be surface-coated with resin or corona treatment to improve the adhesion to printing inks. The coating resin layer may be applied by any method. The resin layer may be one or more of a polyester resin, a polyurethane resin, an acrylic resin, a polyethylene resin, a polypropylene resin, a polyamide resin, and a fluorine-containing resin, which can help improve ink adhesion.

The method for producing the film of the present invention will be described below, but it is not limited to this example. The polyester, modified polypropylene and inorganic particles are thoroughly mixed, dried and transported to an extruder B which has been heated to a temperature of 270 to 300 ° C, and is melted into a polymer B; the polyester and inorganic particles are transported to the Extruder A heated to a temperature of 270 to 300 ° C melted it into polymer A. It is then synthesized into an A / B / A structure through three T die layers to form an unstretched sheet, which is then cooled by a roller. It cures and becomes an unstretched film.

The unstretched film is heated with a roller and infrared rays, and is stretched in the longitudinal direction by using the speed difference of two or more rollers to form a longitudinally stretched film. The longitudinal extension temperature needs to be higher than the glass transition point (Tg) of the polyester in layer B. The longitudinal stretching ratio is preferably 2.5 to 4.0 times, and more preferably 2.7 to 3.5 times. When the stretching ratio is less than 2.5 times, the void cannot be effectively pulled out to achieve lightweight characteristics; when it exceeds 4.0 times, the strength of the film is insufficient, and it is easy to cause fracture in the film formation.

Then, the longitudinally stretched film is clamped by a clamp to perform lateral extension. When the longitudinally stretched film is stretched, a pre-shrinking treatment is performed at the same time, and then a light weight, low shrinkage white polyester film is formed after heat fixing. The lateral extension temperature requires the glass transition point (Tg) of the polyester in layer B. The lateral extension ratio is preferably 2.5 to 4.0 times, more preferably 2.7 to 3.5 times. When the stretching ratio is less than 2.5 times, the void cannot be effectively pulled out to achieve lightweight characteristics; when it exceeds 4.0 times, the strength of the film is insufficient, and it is easy to cause fracture in the film formation.

The thermal fixing temperature is preferably 180 ~ 240 ° C, more preferably 200 ~ 220 ° C. When the temperature is lower than 180 ° C, the heat shrinkability of the film is too large, and the characteristics of low shrinkage cannot be effectively achieved. If the temperature is greater than 240 ° C In this case, although the shrinkage of the film can be effectively reduced, the modified polypropylene will be deformed and the lightweight properties cannot be obtained.

The lightweight and low-shrinkage white polyester film in the present invention needs to have a three-layer structure of A / B / A, in which the total thickness of the two outermost A layers is 2% to 30% of the thickness of the entire film.

The light weight and low shrinkage white polyester film in the present invention has a specific gravity of preferably 0.6 to 1.2, more preferably 0.80 to 1.15. When the specific gravity is less than 0.8, the strength of the film is insufficient due to too many voids, which affects the printability. If the specific gravity exceeds 1.2, it does not have lightweight characteristics.

The present invention will be specifically described by way of examples. But the invention is not limited to these Examples.

Melt Index (MI)

MI is measured according to the ISO-1133 standard method under the conditions of a temperature of 230 ° C and a load of 2.16 kg.

The heat distortion temperature was determined according to the method of ASTM D648.

[Modified polypropylene is prepared in advance] as shown in Table 1

[Modified Polypropylene 1] (PP1)

100 parts by weight of polypropylene, 0.3 parts by weight of 2,5-dimethyl-2,5-di (tertiary-butylperoxy) hexyne, and 0.05 parts by weight of trimethylolpropane triacrylate, and The screw extruder was kneaded and melted to obtain modified polypropylene PP1, which had a heat distortion temperature of 125 ° C and MI = 1g / 10min.

[Modified Polypropylene 2] (PP2)

100 parts by weight of polypropylene, 1 part by weight of 2,5-dimethyl-2,5-di (tertiary-butylperoxy) hexyne, and 0.05 parts by weight of trimethylolpropane triacrylate, and The screw extruder was kneaded and melted to obtain modified polypropylene PP2, and its thermal deformation temperature was 130 ° C and MI = 0.4g / 10min.

[Modified Polypropylene 3] (PP3)

100 parts by weight of polypropylene, 0.05 parts by weight of 2,5-dimethyl-2,5-di (third-butylperoxy) hexyne, and 0.05 parts by weight of trimethylolpropane triacrylate, and The screw extruder was kneaded and melted to obtain modified polypropylene PP3, which had a heat distortion temperature of 115 ° C and MI = 3g / 10min.

[Modified Polypropylene 4] (PP4)

100 parts by weight of polypropylene, 5 parts by weight of 2,5-dimethyl-2,5-di (tertiary-butylperoxy) hexyne, and 0.05 parts by weight of trimethylolpropane triacrylate, and The screw extruder was kneaded and melted to obtain modified polypropylene PP4, and its thermal deformation temperature was 135 ° C and MI = 0.1g / 10min.

[Example 1]

90% by weight of polyethylene terephthalate resin (PET) and 10% by weight of titanium dioxide (TiO2) as raw materials of layer A, 80% by weight of polyethylene terephthalate resin, and 10% by weight Modified polypropylene resin 1 and 10% by weight of titanium dioxide are used as raw materials for layer B. After being melt extruded at 290 ° C and three T die layers, they are synthesized into an A / B / A structure, which is formed after longitudinal extension, lateral extension, and heat fixing Film, where the sum of the thicknesses of the two A layers is 25 μm and the thickness of the B layer is 225 μm. The physical properties of the polyester film are listed in Table 2. .

[Example 2]

An A / B / A structure film was prepared in the same manner as in Example 1, except that the raw material of the B layer was changed to 85% by weight of polyethylene terephthalate resin, 5% by weight of modified polypropylene resin 1 and 10 by weight. % Titanium dioxide, where the sum of the thicknesses of the two A layers is 25 μm and the thickness of the B layer is 225 μm. The physical properties of the polyester film are listed in Table 2.

[Example 3]

A / B / A structural film was prepared in the same manner as in Example 1, but the raw material of layer B was changed to 75% by weight polyethylene terephthalate resin, 15% by weight modified polypropylene resin 1 and 10 by weight. % Titanium dioxide, where the sum of the thicknesses of the two A layers is 25 μm and the thickness of the B layer is 225 μm. The physical properties of the polyester film are listed in Table 2.

[Example 4]

An A / B / A structure film was prepared in the same manner as in Example 1, but the raw material of layer B was changed to 75% by weight of polyethylene terephthalate resin, 15% by weight of modified polypropylene resin 2 and 10 by weight. % Titanium dioxide, where the sum of the thicknesses of the two A layers is 25 μm and the thickness of the B layer is 225 μm. The physical properties of the polyester film are listed in Table 2.

[Example 5]

An A / B / A structure film was prepared in the same manner as in Example 1, except that the raw material of the A layer was changed to 90% by weight of polyethylene terephthalate resin and 10% by weight of barium sulfate (BaSO4), and the raw material of the B layer 80% by weight of polyethylene terephthalate resin, 10% by weight of modified polypropylene resin 1 and 10% by weight of barium sulfate. The physical properties of the polyester film are listed in Table 2. The total thickness of the two A layers is 25 μm, and the thickness of the B layer is 225 μm.

[Example 6]

A / B / A structural film was prepared in the same manner as in Example 1, but the raw material of the A layer was changed to 90% by weight of polyethylene terephthalate resin and 10% by weight of barium sulfate, and the raw material of the B layer by 70% by weight Of polyethylene terephthalate resin, 10% by weight of modified polypropylene resin 1 and 20% by weight of barium sulfate. The physical properties of the polyester film are listed in Table 2. The total thickness of the two A layers is 25 μm, and the thickness of the B layer is 225 μm.

[Example 7]

A / B / A structure film was prepared in the same manner as in Example 1, except that the raw material of the A layer was changed to 90% by weight of polyethylene terephthalate resin and 10% by weight of calcium carbonate (CaCO3), and the raw material of the B layer 80% by weight of polyethylene terephthalate resin, 10% by weight of modified polypropylene resin 1 and 10% by weight of calcium carbonate. The total thickness of the two A layers is 25 μm and the thickness of the B layer is 225 μm. The physical properties of the polyester film are listed in Table 2.

[Example 8]

An A / B / A structure film was prepared in the same manner as in Example 1, except that the raw material of the A layer was changed to 90% by weight of polyethylene naphthalate resin (PEN) and 10% by weight of titanium dioxide, and the raw material of the B layer was by weight 80 % Polyethylene naphthalate resin, 10% by weight modified polypropylene resin1 and 10% by weight of titanium dioxide, in which the total thickness of the two A layers is 25 μm, and the thickness of the B layers is 225 μm. The physical properties of the polyester film are listed in Table 2.

[Comparative Example 1]

A / B / A structural film was prepared in the same manner as in Example 1, but the raw material of layer B was changed to 80% by weight polyethylene terephthalate resin, 10% by weight modified polypropylene resin resin 3, and weight. 10% titanium dioxide, in which the thickness of the two A layers is 25 μm, and the thickness of the B layer is 225 μm. The physical properties of the polyester film are listed in Table 2.

[Comparative Example 2]

A / B / A structural film was prepared in the same manner as in Example 1, but the raw material of layer B was changed to 80% by weight polyethylene terephthalate resin, 10% by weight modified polypropylene resin resin 4 and weight. 10% titanium dioxide, in which the thickness of the two A layers is 25 μm, and the thickness of the B layer is 225 μm. The physical properties of the polyester film are listed in Table 2.

[Comparative Example 3]

A / B / A structure film was prepared in the same manner as in Example 1, but the raw material of layer B was changed to 60% by weight polyethylene terephthalate resin, 30% by weight modified polypropylene resin 1 and 10 by weight. % Titanium dioxide, where the sum of the thicknesses of the two A layers is 25 μm and the thickness of the B layer is 225 μm. The physical properties of the polyester film are listed in Table 2.

[Comparative Example 4]

A / B / A structural film was prepared in the same manner as in Example 1, but the raw material of layer B was changed to 90% by weight of polyethylene terephthalate resin and 10% by weight of modified polypropylene resin 1. The total thickness of the A layers was 25 μm, and the thickness of the B layers was 225 μm. The physical properties of the polyester film are listed in Table 2.

[Comparative Example 5]

The A / B / A structure film was prepared in the same manner as in Example 1, but the total thickness of layer A was adjusted to 3 μm, and the thickness of layer B was adjusted to 247 μm. The physical properties of the polyester film are listed in Table 2.

[Comparative Example 6]

The A / B / A structure film was prepared in the same manner as in Example 1, but the total thickness of layer A was adjusted to 80 μm and the thickness of layer B was 170 μm. The physical properties of the polyester film are listed in Table 2.

Physical property test method

Specific gravity test

The film was cut into a 5.0 cm x 5 cm square and measured with a specific gravity balance. The balance model was Precisa XS 225A-SG.

Heat shrinkage test

In a 150 ° C oven, the film was baked in a tension-free state for 30 minutes, the distance between the calibration points before and after heating was measured, and the longitudinal (MD) shrinkage and transverse (TD) shrinkage were calculated according to the following formulas.

Thermal shrinkage% = ((L0-L) / L0) × 100

L0: Calibration point distance before baking

L: Calibration point distance of baking at 150 ℃ for 30 minutes

Extended film forming

Extend the film by 2.8 to 3.4 times in the longitudinal direction and 3.0 to 3.5 times in the transverse direction. Observe whether the film can be formed stably without cracking for 8 hours.

Table 1: Pre-modified polypropylene resin Unit: parts by weight

*Note:

Thickness (μm): Total thickness of upper and lower layers.

PP1: Modified polypropylene 1. Heat distortion temperature 125 ℃, MI = 1g / 10min

PP2: modified polypropylene 2, heat distortion temperature 130 ° C, MI = 0.4g / 10min

PP3: modified polypropylene3, heat distortion temperature 115 ℃, MI = 3g / 10min

PP4: Modified polypropylene 4, heat distortion temperature 135 ° C, MI = 0.1g / 10min

The present invention further compares Examples 1 and 3, as the proportion of modified polypropylene is increased, the proportion can be further reduced, and the weight reduction effect is reduced, while in Comparative Example 3, the amount of modified polypropylene is added more, although the weight reduction effect is the best, However, the film forming property is not good.

The present invention further compares Example 1 and Comparative Example 1. The thermal deformation temperature of the modified polypropylene does not reach 120 ° C. and the MI is not less than 1. During the stretching, the modified polypropylene cannot achieve the lightweight effect due to the stretching deformation.

The present invention further compares Examples 3, 4 and Comparative Example 2. As the thermal deformation temperature of the modified polypropylene is higher, it is less likely to deform when stretched, and the weight reduction effect is better. When the value is too low, unevenness in the size of the film is formed during film formation, resulting in poor film formation and normal production.

The present invention further compares Example 1 and Comparative Example 4. Without the addition of inorganic particles in the B layer, the specific gravity cannot be effectively reduced to achieve a lightweight effect.

The present invention further compares Example 1, Comparative Examples 5 and 6, and in the case where the thickness of the A layer is less than 2%, the film is broken due to the large voids in the inner layer and the dimensional stability is not good. On the other hand, when the thickness of the A layer is more than 30%, it is difficult to have a lightweight property.

According to a further comparative example of the present invention, special modified polypropylene needs to be added to the B layer to have light weight and good film forming properties.

The thermal shrinkage ratio of the examples and the comparative examples is relatively small, and the dimensional stability is good.

In the case where the thickness of the layer A of Comparative Example 5 is 1.2% and less than 2%, the film is broken due to the large inner layer voids, and the film has poor dimensional stability. In the case where the thickness of the layer A of Comparative Example 6 is 32% and more than 30%, it is difficult to have a lightweight property.

Claims (9)

A lightweight, low-shrink white polyester film that includes a three-layer structure of A / B / A, and the total thickness of the two outermost A layers is 2% to 30% of the overall thickness of the polyester film, which is characterized in that its characteristics include The specific gravity ranges from 0.6 to 1.2, the longitudinal thermal shrinkage is less than 1% after baking at 150 ° C for 30 minutes, and the inside of the layers A and B in the structure contains holes, wherein the A layer is relative to the A layer The total combined amount is composed of 65 ~ 95wt% polyester resin and 5 ~ 35wt% inorganic particles, and the average particle diameter (D50) of the inorganic particles is 0.05-5 microns; the total composition of the B layer relative to the B layer The amount is 50 ~ 90wt% polyester resin, 5 ~ 25wt% modified polypropylene resin and 5 ~ 25wt% inorganic particles, and the average particle diameter (D50) of the inorganic particles is 0.05-5 microns and the modified Polypropylene resin should meet the following conditions: (1) modified with 0.1 ~ 3wt% peroxide crosslinking agent relative to the weight of polypropylene resin, (2) the heat distortion temperature must be above 120 ° C, and (3) the melt index (MI) 0.2 to 1 g / 10 minutes at a temperature of 230 ° C and a load of 2.16 kg. The lightweight and low-shrinkage white polyester film according to item 1 of the scope of the patent application, wherein the inorganic particles in the A layer and the B layer in the structure are selected from one or more of barium sulfate, calcium carbonate, and titanium dioxide. The lightweight and low-shrink white polyester film according to item 1 of the scope of the patent application, wherein the polyester resins in layer A and layer B of the structure are selected from polyethylene terephthalate or polynaphthalene Formate. The lightweight, low-shrinkage white polyester film according to item 1 of the scope of the patent application, wherein the peroxide crosslinking agent is selected from the group consisting of α, α'-bis-third-butyl peroxide-1,4 -Diisopropylbenzene or 2,5-dimethyl-2,5-bis (third-butylperoxy) hexyne. The lightweight low-shrinkage white polyester film according to item 1 of the scope of the patent application, wherein the inorganic particles can be added in advance to a polyester resin or a modified polypropylene resin. The lightweight and low-shrinkage white polyester film as described in item 1 of the scope of the patent application, wherein the average particle diameter (D50) of the inorganic particles of the A layer and the B layer in the structure is 0.2-1 micrometer. The lightweight, low-shrinkage white polyester film as described in item 1 of the scope of the patent application, wherein the modified polypropylene resin of layer B is a propylene homopolymer or a copolymer of propylene and an α -olefin. The lightweight and low-shrinkage white polyester film as described in item 1 of the scope of the patent application, wherein the modified polypropylene resin of the B layer is added in an amount of 8 to 15% by weight relative to the total combined amount of the B layer. The lightweight and low-shrink white polyester film as described in the first item of the patent application scope, wherein the total thickness of the two outermost A layers is 5% to 15% of the overall thickness of the polyester film.