Matt polyester film and preparation method thereof

Abstract

The present invention provides a matte polyester film and a preparation method thereof, and relates to the technical field of polyester films. The preparation method comprises the following steps: S1: drying and pre-crystallizing polyester slices, and then melting and extruding them onto a casting roller, and peeling them off after casting to obtain a thick polyester film; S2: longitudinally stretching the thick polyester film after preheating to obtain a polyester unidirectional film; S3: online coating an aqueous matte coating liquid on at least one side of the polyester unidirectional film, and then sequentially preheating, transversely stretching, shaping and coating curing to obtain a matte polyester film including a matte coating. The preparation method of the matte polyester film provided by the present invention prepares the matte coating by coating an aqueous matte coating liquid, and the prepared polyester film can have a lower surface gloss without adding a matte masterbatch, so that the matte effect can be achieved without damaging the mechanical properties of the polyester film, and the prepared matte polyester film can have both a matte effect and mechanical properties.

Description

Technical Field

[0001] The invention relates to the technical field of polyester films, and in particular to a matte polyester film and a preparation method thereof. Background Art

[0002] Matt polyester film has a low surface gloss and comfortable visual effect. It is widely used in release film, car cover film, copper clad laminate, home floor film and other fields. Generally, matte polyester film is made by melt-extruding a mixture of matte masterbatch and polyester base material and then biaxially stretching. The gloss of the matte polyester film made by this method is determined by the content of the matte masterbatch. In order to reduce the gloss of the film, a high proportion of matte masterbatch needs to be added. However, the increase of matte masterbatch will greatly reduce the mechanical strength of the film, making it difficult for the matte polyester film to have both matte effect and mechanical properties. Summary of the invention

[0003] The technical problem to be solved by the present invention is: in order to solve the problem that it is difficult for matte polyester films in the prior art to have a balance between matte effect and mechanical properties, the present invention provides a method for preparing a matte polyester film. The preparation method improves the matte effect of the polyester film without damaging the mechanical properties of the polyester film by coating an aqueous matte coating liquid on at least one side of a polyester slice, thereby solving the problem that it is difficult for matte polyester films in the prior art to have a balance between matte effect and mechanical properties.

[0004] The technical solution adopted by the present invention to solve its technical problem is:

[0005] A method for preparing a matte polyester film comprises the following steps:

[0006] S1: drying and pre-crystallizing the polyester chips, and then melting and extruding them onto a casting roll, and peeling them off after casting to obtain a polyester thick sheet;

[0007] S2: longitudinally stretching the polyester thick sheet after preheating to obtain a polyester unidirectional sheet;

[0008] S3: After the aqueous matte coating liquid is online coated on at least one side of the polyester unidirectional sheet, preheating, transverse stretching, shaping and coating curing are sequentially performed to obtain a matte polyester film including a matte coating.

[0009] Optionally, the aqueous matte coating liquid comprises the following components in parts by weight:

[0010]

[0011] Optionally, the waterborne polyurethane resin is an anionic waterborne polyurethane resin; the solid content of the waterborne polyurethane resin ranges from 25% to 45%.

[0012] Optionally, the solid content of the water-based acrylic resin ranges from 40% to 45%.

[0013] Optionally, the solid content of the water-based matte resin ranges from 30% to 35%.

[0014] Optionally, the high temperature curing agent is selected from at least one of Bayhydur 3100, Desmodur DN, and ELECUT C-K08.

[0015] Optionally, the wetting and leveling agent is selected from BYK-3560, Surfynol 104, At least one of GA-100; the defoamer is selected from SN-Defoamer 777, At least one of Antifoam 2-89; the anti-adhesive agent is selected from Glide 492, At least one of TM-50.

[0016] Optionally, the matte coating has a thickness of 0.02 μm to 2 μm.

[0017] Optionally, step S1 includes: drying and pre-crystallizing the polyester chips and then melt-extruding them, casting them on a casting roller at 15°C to 40°C and then peeling them off to obtain a polyester thick sheet; step S2 includes: preheating the polyester thick sheet at 65°C to 90°C, and longitudinally stretching it 2.8 to 3.5 times to obtain a polyester unidirectional sheet; step S3 includes: after online coating of an aqueous matte coating liquid on at least one side of the polyester unidirectional sheet, preheating it in a transverse stretching preheating area at 85°C to 115°C, then transversely stretching it at a temperature of 110°C to 140°C, shaping and coating curing it at a temperature of 225°C to 245°C, and then pulling, winding, and slitting to obtain a matte polyester film including a matte coating.

[0018] Another object of the present invention is to provide a matte polyester film prepared by the above-mentioned method for preparing the matte polyester film.

[0019] The beneficial effects of the present invention are:

[0020] The method for preparing a matte polyester film provided by the present invention prepares a matte coating by coating an aqueous matte coating liquid, so that the prepared polyester film can have a lower surface gloss without adding a matte masterbatch, thereby achieving a matte effect without damaging the mechanical properties of the polyester film, and further enabling the prepared matte polyester film to have both a matte effect and mechanical properties. DETAILED DESCRIPTION

[0021] The present invention is now further described in detail. The embodiments described below are exemplary and intended to be used to explain the present invention, but cannot be understood as limiting the present invention. All other embodiments obtained by ordinary technicians in this field without creative work based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0022] In order to solve the problem that it is difficult to obtain both matte effect and mechanical properties of matte polyester films in the prior art, the present invention provides a method for preparing a matte polyester film, comprising the following steps:

[0023] S1: drying and pre-crystallizing the polyester chips, and then melting and extruding them onto a casting roll, and peeling them off after casting to obtain a polyester thick sheet;

[0024] S2: preheating the polyester thick sheet and then longitudinally stretching it to obtain a polyester unidirectional sheet;

[0025] S3: After coating the aqueous matte coating liquid online on at least one side of the polyester unidirectional sheet, preheating, transverse stretching, shaping and coating curing are sequentially performed to obtain a matte polyester film including a matte coating.

[0026] The method for preparing a matte polyester film provided by the present invention prepares a matte coating by coating an aqueous matte coating liquid, so that the prepared polyester film can have a lower surface gloss without adding a matte masterbatch, thereby achieving a matte effect without damaging the mechanical properties of the polyester film, and further enabling the prepared matte polyester film to have both a matte effect and mechanical properties.

[0027] In order to ensure the matte effect of the polyester film, the aqueous matte coating liquid of the present invention preferably comprises the following components in parts by weight:

[0028]

[0029] The water-based matte coating liquid does not contain a high content of large-particle matte masterbatch. Through the synergistic effect of water-based polyurethane, water-based acrylic resin, water-based matte resin and various additives, the coating prepared by the water-based matte coating liquid not only gives the polyester film surface an excellent matte effect, but also has excellent adhesion to the polyester film substrate, and does not affect the mechanical properties of the polyester film.

[0030] In the preparation process of the existing matte polyester film, the increase of matte masterbatch will not only lead to a decrease in the mechanical properties of the film, but also, with the increase in the addition ratio of the matte masterbatch, the degree of decrease in the surface gloss of the polyester film will be significantly slowed down. That is to say, in the scheme of preparing the matte polyester film by using the matte masterbatch, with the increase in the addition ratio of the matte masterbatch, even if the mechanical properties of the polyester film are not considered, the surface gloss will not be infinitely reduced. Therefore, in the technical scheme of preparing the matte polyester film by adding the matte masterbatch, the gloss of the matte polyester film is difficult to reach an ultra-low level (haze>99%, gloss<8GU, (60°)); in addition, the matte masterbatch also has the problem of uneven dispersion during the preparation process, resulting in poor uniformity of the film gloss, which cannot meet the needs of high-end applications; and adding a large amount of matte masterbatch on the surface of the polyester film will significantly reduce the adhesion of the film, which will affect subsequent processing.

[0031] The water-based matte coating liquid provided by the present invention forms a matte layer after online coating by introducing a water-based matte resin, based on the fact that the water-based matte resin is a self-matting resin. Since the water-based matte resin does not contain matting powder, the increase of the water-based matte resin will not cause damage to the mechanical properties of the polyester film. Therefore, the addition amount of the water-based matte resin can be adjusted according to demand, thereby adjusting the glossiness of the surface of the polyester film, and then a matte polyester film with ultra-low gloss can be obtained. Compared with the solution of introducing matte powder, the gloss uniformity of the polyester film is more excellent.

[0032] The water-based matte coating liquid contains polyurethane resin, which has good adhesion to polyester film and downstream processing coating, helping to improve the yield rate of downstream processing.

[0033] In order to take into account both the matte properties and mechanical properties of the matte polyester film, the present invention preferably uses an anionic waterborne polyurethane resin as the waterborne polyurethane resin, so that the anionic groups introduced into the polyurethane chain can make the waterborne polyurethane resin sufficiently hydrophilic, thereby ensuring the stability of the waterborne matte coating liquid; the present invention further preferably uses the solid content of the waterborne polyurethane resin in the range of 25wt%-45wt%, and specifically preferably uses the waterborne polyurethane resin selected from ETERNACOLL UW-5502 (made by UBE), VR-001 (DIC), 140AQ (Bayer) at least one; preferably the solid content of the aqueous acrylic resin is in the range of 40wt%-45wt%, and the aqueous acrylic resin is specifically preferably selected from PRIMAL 3208 (DOW), A 2227 / 1 (manufactured by Bayer), Antkote 2036 (manufactured by Wanhua Chemical); preferably, the solid content range of the water-based matte resin is 30%-35%, and specifically preferably, the water-based matte resin is selected from at least one of Neorez R-1010 (manufactured by DSM), HY-5306 (manufactured by Huiyou Technology), and Allnex 6795 (manufactured by Allnex, Germany).

[0034] In the present invention, the high temperature curing agent is preferably selected from at least one of Bayhydur 3100 (manufactured by Bayer), Desmodur DN (manufactured by Covestro), and ELECUT C-K08 (manufactured by TAKEMOTO); the wetting and leveling agent is preferably selected from BYK-3560 (manufactured by BYK), Surfynol 104 (manufactured by Nissin-chem), GA-100 (manufactured by Evonik); preferably, the defoamer is selected from SN-Defoamer 777 (manufactured by Sannopco), Antifoam 2-89 (made by Evonik) or at least one thereof; preferably the anti-blocking agent is selected from Glide 492 (made by Evonik), At least one of TM-50 (manufactured by Grace).

[0035] The thickness of the matte coating in the matte polyester film of the present invention is preferably 0.02 μm to 2 μm, and further preferably 0.1 μm to 1.5 μm. On the one hand, it is to avoid that the coating thickness is too thin, resulting in high gloss and affecting the matte effect; on the other hand, it is to avoid that the coating thickness is too thick, resulting in incomplete curing and affecting the matte effect and mechanical properties.

[0036] The polyester chips in the present invention are bulk raw materials, and the brand and manufacturer are not limited.

[0037] Specifically, step S1 in the present invention comprises: drying and pre-crystallizing the polyester slices and then melt-extruding them, casting them on a casting roller at 15°C to 40°C and then peeling them off to obtain a polyester thick sheet; step S2 comprises: preheating the polyester thick sheet at 65°C to 90°C, and longitudinally stretching it by 2.8 to 3.5 times to obtain a polyester unidirectional sheet; step S3 comprises: online coating of an aqueous matte coating liquid on at least one side of the polyester unidirectional sheet, preheating it in a transverse stretching preheating area at 85°C to 115°C, then transversely stretching it at a temperature of 110°C to 140°C, shaping it at a temperature of 225°C to 245°C and curing the coating, and then pulling, winding, and slitting to obtain a matte polyester film including a matte coating.

[0038] The present invention obtains a unidirectional sheet by drying and then melt-extruding the polyester slices, casting and longitudinally stretching them, coating one or both sides of the unidirectional sheet with a layer of water-based matte coating liquid online, and obtaining an online coated ultra-low gloss polyester film after transverse stretching, shaping and coating curing, and then packaging and warehousing after traction, winding and slitting. This technology does not contain a high content of large-particle matte masterbatch, and will not reduce the mechanical properties of the polyester film; the water-based matte coating liquid contains polyurethane resin, which has good adhesion to the polyester film and downstream processing coating, and improves the yield rate of downstream processing; matte resin is added to the water-based matte coating liquid, which does not contain matte powder and is a self-matting resin. The matte layer formed after online coating can adjust the gloss according to demand, and can obtain an ultra-low gloss polyester film, and the gloss uniformity of the polyester film is excellent.

[0039] Another object of the present invention is to provide a matte polyester film prepared by the above-mentioned method for preparing the matte polyester film.

[0040] The matte polyester film provided by the present invention is prepared by coating an aqueous matte coating liquid to prepare a matte coating, so that the prepared polyester film can have a lower surface gloss without adding a matte masterbatch, thereby being able to achieve a matte effect without damaging the mechanical properties of the polyester film, thereby enabling the prepared matte polyester film to have both a matte effect and mechanical properties.

[0041] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below.

[0042] Example 1

[0043] This embodiment provides a method for preparing a matte polyester film, comprising the following steps:

[0044] S1: After drying and pre-crystallization, the polyester chips are melt-extruded onto a 20°C casting roll, and then peeled off after casting to obtain a polyester thick sheet;

[0045] S2: preheating the polyester thick sheet at 70-82°C and then longitudinally stretching it 3.25 times to obtain a polyester unidirectional sheet;

[0046] S3: After coating the water-based matte coating liquid on one or both sides of the polyester unidirectional sheet online, preheating at 85-110° C., transverse stretching at 115-125° C., shaping at 230-240° C. and coating curing are performed in sequence to obtain a matte polyester film including a matte coating.

[0047] The composition of the aqueous matte coating liquid is shown in Table 1 according to weight fraction.

[0048] Example 2

[0049] This embodiment provides a method for preparing a matte polyester film, comprising the following steps:

[0050] S1: After drying and pre-crystallization, the polyester chips are melt-extruded onto a 15°C casting roll, and then peeled off after casting to obtain a polyester thick sheet;

[0051] S2: preheating the polyester thick sheet at 65°C and then longitudinally stretching it 2.8 times to obtain a polyester unidirectional sheet;

[0052] S3: After coating the water-based matte coating liquid on one or both sides of the polyester unidirectional sheet online, preheating at 85° C., transverse stretching at 110° C., shaping at 225° C. and coating curing are performed in sequence to obtain a matte polyester film including a matte coating.

[0053] The composition of the aqueous matte coating liquid is shown in Table 1 according to weight fraction.

[0054] Example 3

[0055] This embodiment provides a method for preparing a matte polyester film, comprising the following steps:

[0056] S1: After drying and pre-crystallization, the polyester chips are melt-extruded onto a 40°C casting roll, and then peeled off after casting to obtain a polyester thick sheet;

[0057] S2: preheating the polyester thick sheet at 90°C and then longitudinally stretching it 3.5 times to obtain a polyester unidirectional sheet;

[0058] S3: After coating the water-based matte coating liquid on one side or both sides of the polyester unidirectional sheet online, preheating at 115° C., transverse stretching at 140° C., shaping at 245° C. and coating curing are performed in sequence to obtain a matte polyester film including a matte coating.

[0059] The composition of the aqueous matte coating liquid is shown in Table 1 according to weight fraction.

[0060] Comparative Example 1

[0061] A 50 μm extruded matte polyester film (Wanhua HMF07DC-2) available on the market was selected to test its performance.

[0062] Comparative Example 2

[0063] A 75 μm extruded matte polyester film (Wanhua HMF07DC-2) available on the market was selected to test its performance.

[0064] The difference between Comparative Examples 3-11 and Example 1 is that the composition of the aqueous matte coating liquid is shown in Table 1, based on weight fraction.

[0065] Table 1

[0066]

[0067] The polyester films prepared in the above embodiments and comparative examples were tested for performance, and the testing method was as follows:

[0068] 1. Thickness test method

[0069] Cut three films of about 100mm width along the width direction of the sample. The sample should not have wrinkles or other defects. Measure the thickness of the sample according to the requirements of ISO4593:1993. Measure 27 points at equal distances on the sample, and the distance between two measuring points should be no less than 50mm. For uncut film rolls, the measuring point should be 50mm away from the edge of the film, and for cut rolls, the adjustment point should be 2mm away from the edge of the film. Take the average of the 27 measured values ​​as the test result.

[0070] 2. Transmittance and haze test methods

[0071] The test was conducted using NIPPON DENSHOKU NDH5000 in accordance with the method specified in ASTM D1003.

[0072] 3. Gloss test method

[0073] The test was carried out using a BYK-4561 gloss meter according to the method specified in DIN 67530.

[0074] 4. Tensile strength and elongation at break test methods

[0075] The C610M intelligent electronic tensile testing machine produced by Jinan Languang Electromechanical Technology Co., Ltd. was used for testing according to the method specified in GB / T13542.2-2021.

[0076] 5. Adhesion test method

[0077] Use BYK-5123 white grid knife and test according to ASTM D3359.

[0078] The test results are shown in Table 2:

[0079] Table 2

[0080]

[0081] It can be seen from the data in the above table that the matte polyester films prepared in various embodiments of the present invention have ultra-low gloss, a small gloss fluctuation range in the entire range, good mechanical properties, and good adhesion for further release or ink printing on the surface of the film, and have both excellent matte effect and mechanical properties.

[0082] Comparative Examples 1 and 2 both use existing commercially available extruded matte polyester films. Compared with Example 1, the matte effect, mechanical properties and adhesion are all poor.

[0083] Compared with Example 1, in Comparative Example 3, no water-based polyurethane resin was added to the water-based matte coating liquid, and the gloss of the prepared polyester film was high, the gloss fluctuation range was large, and the adhesion was poor.

[0084] In Comparative Example 4, compared with Example 1, the amount of water-based polyurethane resin added to the water-based matte coating liquid is increased, and the gloss of the prepared polyester film is higher, the gloss fluctuation range is larger, and the adhesion is poor.

[0085] Comparative Example 5 Compared with Example 1, HYDRAN AP-40F (manufactured by DIC) was used to replace the waterborne polyurethane resin ETERNACOLL UW-5502 in the waterborne matte coating liquid. The prepared polyester film had lower transmittance, higher gloss, larger gloss fluctuation range, and poorer adhesion.

[0086] Compared with Example 1, in Comparative Example 6, no water-based acrylic resin was added to the water-based matte coating liquid, and the prepared polyester film had a higher gloss, a larger gloss fluctuation range, and poorer adhesion.

[0087] In Comparative Example 7, compared with Example 1, the amount of water-based acrylic resin added to the water-based matte coating liquid is increased, and the gloss of the prepared polyester film is higher, the gloss fluctuation range is larger, and the adhesion is poor.

[0088] In Comparative Example 8, compared with Example 1, Neocryl A-1110 (manufactured by DSM) was used to replace the water-based acrylic resin PRIMAL 3208 in the water-based matte coating liquid. The prepared polyester film had reduced light transmittance, higher gloss, a larger gloss fluctuation range, and poorer adhesion.

[0089] Compared with Example 1, Comparative Example 9 reduces the amount of water-based matte resin added in the water-based matte coating liquid, and the prepared polyester film has reduced haze, higher gloss, and a larger gloss fluctuation range.

[0090] In Comparative Example 10, compared with Example 1, the amount of water-based matte resin added to the water-based matte coating liquid is increased, and the gloss fluctuation range of the prepared polyester film is larger.

[0091] Compared with Example 1, ACURE 871 (manufactured by Yuanhe Chemical Industry) was used to replace the water-based matte resin Neorez R-1010 in the water-based matte coating liquid. The glossiness of the prepared polyester film was higher and the glossiness fluctuation range was larger.

[0092] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for preparing a matte polyester film, characterized in that: The steps include: S1: drying and pre-crystallizing the polyester chips, and then melting and extruding them onto a casting roll, and peeling them off after casting to obtain a polyester thick sheet; S2: longitudinally stretching the polyester thick sheet after preheating to obtain a polyester unidirectional sheet; S3: after coating the at least one side of the polyester unidirectional sheet with an aqueous matte coating liquid online, preheating, transverse stretching, shaping and coating curing are sequentially performed to obtain a matte polyester film including a matte coating; The aqueous matte coating liquid comprises the following components in parts by weight: 5-18 parts of waterborne polyurethane resin; 10-15 parts of water-based acrylic resin; 30-50 parts of water-based matte resin; High temperature curing agent 1-10 parts; Wetting and leveling agent 0.03-1 part; Defoaming agent 0.05-0.08 parts; 2-7 parts of anti-adhesion agent; 50-60 parts of deionized water; The waterborne polyurethane resin is an anionic waterborne polyurethane resin; the solid content of the waterborne polyurethane resin is in the range of 25%-45%; the waterborne polyurethane resin is selected from at least one of ETERNACOLL UW-5502 (manufactured by UBE) and HYDRAN® VR-001 (manufactured by DIC); The solid content of the water-based acrylic resin is in the range of 40%-45%; the water-based acrylic resin is selected from at least one of PRIMAL 3208 (manufactured by DOW) and BAYHYDROL® A 2227 / 1 (manufactured by Bayer); The solid content of the water-based matte resin is in the range of 30%-35%; the water-based matte resin is selected from at least one of Neorez R-1010 (manufactured by DSM) and HY-5306 (manufactured by Huiyou Technology).

2. The method for preparing a matte polyester film according to claim 1, characterized in that: The high temperature curing agent is selected from at least one of Bayhydur 3100, Desmodur DN, and ELECUT C-K08.

3. The method for preparing a matte polyester film according to claim 1, characterized in that: The wetting and leveling agent is selected from at least one of BYK-3560, Surfynol 104, and Carbowet® GA-100; the defoamer is selected from at least one of SN-Defoamer777 and TEGO® Antifoam 2-89; and the anti-blocking agent is selected from at least one of TEGO® Glide 492 and LUDOX® TM-50.

4. The method for preparing a matte polyester film according to any one of claims 1 to 3, characterized in that: The thickness of the matte coating is 0.02 μm to 2 μm.

5. The method for preparing the matte polyester film according to any one of claims 1 to 3, characterized in that: Step S1 comprises: drying and pre-crystallizing the polyester slices, then melt-extruding them, casting them on a casting roller at 15°C-40°C, and then peeling them off to obtain a polyester thick sheet; step S2 comprises: preheating the polyester thick sheet at 65°C-90°C, and longitudinally stretching them by 2.8-3.5 times to obtain a polyester unidirectional sheet; step S3 comprises: online coating at least one side of the polyester unidirectional sheet with an aqueous matte coating liquid, preheating them in a transverse stretching preheating area at 85°C-115°C, then transversely stretching them at a temperature of 110°C-140°C, shaping them at a temperature of 225°C-245°C and curing the coating, and then pulling, winding, and slitting them to obtain a matte polyester film including a matte coating.

6. A matte polyester film, characterized in that: The matte polyester film is prepared by the method for preparing the matte polyester film according to any one of claims 1 to 5.

Images