PET cast film and preparation method thereof

Abstract

The invention discloses a preparation method of a PET cast film. The preparation method comprises the following steps: step S1, drying raw materials PBT, PETG, APET and SiO2 master batch; s2, the PBT, the PETG, the APET and the SiO2 master batch are sequentially subjected to plasticizing melting, filtering, sheet casting, crystallization shaping, corona and rolling according to a preset multi-layer film structure, and the PET cast film with the multi-layer film structure is obtained; wherein the crystallization shaping specifically comprises the steps that the film subjected to online thickness measurement is sequentially wound on a plurality of rollers which are arranged in a staggered mode, the temperature of the roller located at the starting end is 35 DEG C, the temperature of the roller located at the tail end is 75 DEG C, and the temperatures of the other rollers are sequentially increased between 35 DEG C and 80 DEG C according to the arrangement direction. Compared with the prior art, the crystallization and shaping step is set between the casting piece and the corona, and the PBT and the APET can be further efficiently crystallized through the specific operation of crystallization and shaping, so that the stability of the formed PET cast film is improved, and deformation and shrinkage are avoided.

Description

Technical Field

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

[0002] At present, the products on the market are all biaxially stretched PET films, namely BOPET. The market scale is large, and the products are single, with overcapacity and single performance. In some specific application fields, PET films with larger stretching are required, but there is less research on this type of film. Summary of the invention

[0003] In view of the deficiencies in the prior art, the object of the present invention is to provide a PET cast film and a preparation method thereof, so as to solve the problem that the performance of the PET film is single in the prior art.

[0004] To achieve the above object, the first aspect of the present invention adopts the following technical solution: a method for preparing a PET cast film, comprising the following steps:

[0005] Step S1, drying raw materials PBT, PETG, APET and SiO2 masterbatch;

[0006] Step S2, plasticizing, melting, filtering, casting, crystallizing, corona treatment and winding the PBT, PETG, APET and SiO2 masterbatch in an orderly manner according to a preset multi-layer film structure to obtain a PET cast film with a multi-layer film structure;

[0007] Wherein, the crystallization shaping specifically includes:

[0008] The film formed by the casting sheet is wound on multiple rollers arranged in a staggered manner. The temperature of the roller at the starting end is 35°C and the temperature of the roller at the end is 80°C. The temperatures of the remaining rollers increase successively between 35°C and 80°C according to the arrangement direction.

[0009] Further, the step S2 specifically includes:

[0010] Step S21, taking part of the dried PBT and PETG to mix to form an A layer material, taking part of the dried PETG as a B layer material, taking part of the dried PBT, APET and SiO2 masterbatch to mix to form a C layer material;

[0011] Step S22, according to the preset multi-layer film structure, the A layer material, the B layer material and the C layer material are sequentially fed into the corresponding extruder for plasticization and melting, and then filtered and then fed into the multi-channel die head for extrusion, and the extrudate is cooled by a chilled roller to form a casting sheet;

[0012] Step S23, the cast sheet is sequentially subjected to crystallization shaping, corona treatment and winding to obtain a PET cast film having a multi-layer film structure.

[0013] Furthermore, there are five rollers, and the temperatures of the three rollers between the roller at the starting end and the roller at the end are 45° C., 55° C. and 65° C. respectively.

[0014] Further, the step S23 is specifically as follows:

[0015] According to the preset three-layer film structure, the A layer material, B layer material and C layer material are sequentially fed into the corresponding extruder for plasticization and melting, and then filtered and then extruded into a three-channel die head in the distribution manner of A layer material, B layer material and C layer material from bottom to top. The extrudate is cooled into a casting sheet by a chilled roller.

[0016] Further, the step S23 is specifically as follows:

[0017] According to the preset five-layer membrane structure, the A layer material, B layer material and C layer material are sequentially fed into the corresponding extruder for plasticization and melting, and then filtered and then extruded into a five-channel die head in the distribution manner of A layer material, C layer material, B layer material, C layer material and A layer material from bottom to top. The extrudate is cooled into a casting sheet by a chilled roller.

[0018] Furthermore, the A layer material includes PBT and PETG, and the mass ratio of PBT to PETG is 3:7, the B layer material includes PETG, and the C layer material includes PBT, APET and SiO2 masterbatch, and the mass ratio of PBT, APET and SiO2 masterbatch is 6.8:3:0.2.

[0019] Furthermore, the extrusion temperature of the extruder corresponding to the A layer material and the B layer material is 220-240°C, the extrusion temperature of the extruder corresponding to the C layer material is 240-260°C, and the temperature of the multi-channel die head is 250°C.

[0020] Furthermore, an online thickness measurement is provided between the casting and the crystallization forming.

[0021] The second aspect of the present invention adopts the following technical solution: a PET cast film is prepared by the preparation method of a PET cast film described in the first aspect of the present invention.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention uses PBT, PETG, APET and SiO2 masterbatch as raw materials for compounding, and in the processing process, mainly sets the process step of crystallization and shaping between the casting sheet and the corona. The specific operation of crystallization and shaping enables PBT and APET to be further crystallized efficiently, thereby improving the stability of the formed PET cast film without deformation and shrinkage.

[0024] 2. Solved the problem that double-stretched PET, i.e. BOPET, cannot be deep-stretched, to meet the market demand for special product technology;

[0025] 3. The PET cast film prepared by the present invention has high transparency, is easy to be blister-formed and deep-drawn, can be heat-sealed and has good folding and forming properties. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below through specific embodiments:

[0027] Example 1

[0028] Step S1: PBT, PETG, APET and SiO2 masterbatch are placed in different vacuum drum dryers for drying, respectively, with a steam pressure of 0.1-0.25MPa, a vacuum degree of 70-80kPa, and a drying time of 3-4h;

[0029] Step S2: 30 parts of PBT and 70 parts of PETG are mixed as A layer material, and then the A layer material is added to the No. 1 extruder for plasticization and melting. At this time, the extrusion temperature in the No. 1 extruder is 240° C., and then enters the die head through a coarse filter, a metering pump, a fine filter and a static mixer;

[0030] Step S3: 98 parts of PETG are mixed as the B layer material, and then the B layer material is added to the No. 2 extruder for plasticization and melting. At this time, the extrusion temperature in the No. 2 extruder is 220° C., and then enters the die head through a coarse filter, a metering pump, a fine filter and a static mixer;

[0031] Step S4: 68 parts of PBT, 30 parts of APET and 2 parts of SiO2 masterbatch are mixed as C layer material, and then the C layer material is added to the No. 3 extruder for plasticization and melting. At this time, the extrusion temperature in the No. 3 extruder is 250° C., and then enters the die head through a coarse filter, a metering pump, a fine filter and a static mixer;

[0032] Step S5: extruding the high-temperature melt formed in steps 2, 3 and 4 through a three-channel die head at a temperature of 250° C., placing the extrudate on a chilled roller, and rapidly cooling it to form a cast sheet;

[0033] Step S6: performing online thickness measurement, crystallization shaping, corona treatment and winding on the cast sheet in sequence, and finally obtaining a PET cast film having a three-layer structure of layer A, layer B and layer C arranged in sequence from bottom to top;

[0034] Among them, the crystallization shaping specifically includes: winding the film after online thickness measurement on 5 rollers arranged in sequence, and the temperatures of the 5 rollers are arranged to be 35°C, 45°C, 55°C, 65°C and 80°C from the roller at the starting end to the roller at the end.

[0035] Example 2

[0036] Step S1: PBT, PETG, APET and SiO2 masterbatch are placed in different vacuum drum dryers for drying, respectively, with a steam pressure of 0.1-0.25MPa, a vacuum degree of 70-80kPa, and a drying time of 3-4h;

[0037] Step S2: 30 parts of PBT and 70 parts of PETG are mixed as A layer material, and then the A layer material is added to the No. 1 extruder for plasticization and melting. At this time, the extrusion temperature in the No. 1 extruder is 230° C., and then enters the die head through a coarse filter, a metering pump, a fine filter and a static mixer;

[0038] Step S3: 68 parts of PBT, 30 parts of APET and 2 parts of SiO2 masterbatch are mixed as C layer material, and then the C layer material is added to the No. 2 extruder for plasticization and melting. At this time, the extrusion temperature in the No. 2 extruder is 240° C., and then enters the die head through a coarse filter, a metering pump, a fine filter and a static mixer;

[0039] Step S4: 98 parts of PETG are mixed as the B layer material, and then the B layer material is added to the No. 3 extruder for plasticization and melting. At this time, the extrusion temperature in the No. 3 extruder is 240° C., and then enters the die head through a coarse filter, a metering pump, a fine filter and a static mixer;

[0040] Step S5: forming the high temperature melt formed in step 2 into two strands, forming the high temperature melt formed in step 3 into two strands, and then the two strands of high temperature melt formed in step 2, the two strands of high temperature melt formed in step 3 and the high temperature melt formed in step 4 are sequentially arranged from bottom to top into a layer A material, a layer C material, a layer B material, a layer C material and a layer A material and are extruded into a five-flow channel die head, wherein the temperature of the five-flow channel die head is 250° C., and the extrudate is adhered to a chilling roller and rapidly cooled to form a cast sheet;

[0041] Step S6: The cast sheet is subjected to online thickness measurement, crystallization shaping, corona treatment and winding in sequence, and then a PET cast film having a five-layer structure of layer A, layer C, layer B, layer C and layer A arranged in sequence from bottom to top is obtained;

[0042] Among them, the crystallization shaping specifically includes: winding the film after online thickness measurement on 5 rollers arranged in sequence, and the temperatures of the 5 rollers are arranged to be 35°C, 45°C, 55°C, 65°C and 80°C from the roller at the starting end to the roller at the end.

[0043] Example 3

[0044] Step S1: PBT, PETG, APET and SiO2 masterbatch are placed in different vacuum drum dryers for drying, respectively, with a steam pressure of 0.1-0.25MPa, a vacuum degree of 70-80kPa, and a drying time of 3-4h;

[0045] Step S2: 30 parts of PBT and 70 parts of PETG are mixed as A layer material, and then the A layer material is added to the No. 1 extruder for plasticization and melting. At this time, the extrusion temperature in the No. 1 extruder is 220° C., and then enters the die head through a coarse filter, a metering pump, a fine filter and a static mixer;

[0046] Step S3: 98 parts of PETG are mixed as the B layer material, and then the B layer material is added to the No. 2 extruder for plasticization and melting. At this time, the extrusion temperature in the No. 2 extruder is 230° C., and then enters the die head through a coarse filter, a metering pump, a fine filter and a static mixer;

[0047] Step S4: 68 parts of PBT, 30 parts of APET and 2 parts of SiO2 masterbatch are mixed as C layer material, and then the C layer material is added to the No. 3 extruder for plasticization and melting. At this time, the extrusion temperature in the No. 3 extruder is 240° C., and then enters the die head through a coarse filter, a metering pump, a fine filter and a static mixer;

[0048] Step S5: extruding the high-temperature melt formed in steps 2, 3 and 4 through a three-channel die head at a temperature of 250° C., placing the extrudate on a chilled roller, and rapidly cooling it to form a cast sheet;

[0049] Step S6: performing online thickness measurement, crystallization shaping, corona treatment and winding on the cast sheet in sequence, and finally obtaining a PET cast film having a three-layer structure of layer A, layer B and layer C arranged in sequence from bottom to top;

[0050] Among them, the crystallization shaping specifically includes: winding the film after online thickness measurement on 5 rollers arranged in sequence, and the temperatures of the 5 rollers are arranged to be 35°C, 45°C, 55°C, 65°C and 80°C from the roller at the starting end to the roller at the end.

[0051] Comparative Example 1

[0052] Step S1: PBT, PETG, APET and SiO2 masterbatch are placed in different vacuum drum dryers for drying, respectively, with a steam pressure of 0.1-0.25MPa, a vacuum degree of 70-80kPa, and a drying time of 3-4h;

[0053] Step S2: 30 parts of PBT and 70 parts of PETG are mixed as A layer material, and then the A layer material is added to the No. 1 extruder for plasticization and melting. At this time, the extrusion temperature in the No. 1 extruder is 220° C., and then enters the die head through a coarse filter, a metering pump, a fine filter and a static mixer;

[0054] Step S3: 98 parts of PETG are mixed as the B layer material, and then the B layer material is added to the No. 2 extruder for plasticization and melting. At this time, the extrusion temperature in the No. 2 extruder is 230° C., and then enters the die head through a coarse filter, a metering pump, a fine filter and a static mixer;

[0055] Step S4: 68 parts of PBT, 30 parts of APET and 2 parts of SiO2 masterbatch are mixed as C layer material, and then the C layer material is added to the No. 3 extruder for plasticization and melting. At this time, the extrusion temperature in the No. 3 extruder is 240° C., and then enters the die head through a coarse filter, a metering pump, a fine filter and a static mixer;

[0056] Step S5: extruding the high-temperature melt formed in steps 2, 3 and 4 through a three-channel die head at a temperature of 250° C., placing the extrudate on a chilled roller, and rapidly cooling it to form a cast sheet;

[0057] Step S6: The cast sheet is subjected to online thickness measurement, corona treatment and winding in sequence, and then a PET cast film having a three-layer structure of layer A, layer B and layer C arranged in sequence from bottom to top is obtained.

[0058] The PET cast films prepared in the above Examples 1 to 4 and Comparative Example 1 were tested and the data are shown in the following table.

[0059]

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a PET cast film, characterized in that: The following steps are involved: Step S1, drying raw materials PBT, PETG, APET and SiO2 masterbatch; Step S2, plasticizing, melting, filtering, casting, crystallizing, corona treatment and winding the PBT, PETG, APET and SiO2 masterbatch in an orderly manner according to a preset multi-layer film structure to obtain a PET cast film with a multi-layer film structure; Wherein, the crystallization shaping specifically includes: The film formed by the casting sheet is wound on multiple rollers arranged in a staggered manner. The temperature of the roller at the starting end is 35°C and the temperature of the roller at the end is 80°C. The temperatures of the remaining rollers increase successively between 35°C and 80°C according to the arrangement direction.

2. The method for preparing a PET cast film according to claim 1, characterized in that: The step S2 specifically includes: Step S21, taking part of the dried PBT and PETG to mix to form an A layer material, taking part of the dried PETG as a B layer material, taking part of the dried PBT, APET and SiO2 masterbatch to mix to form a C layer material; Step S22, according to the preset multi-layer film structure, the A layer material, the B layer material and the C layer material are sequentially fed into the corresponding extruder for plasticization and melting, and then filtered and then fed into the multi-channel die head for extrusion, and the extrudate is cooled by a chilled roller to form a casting sheet; Step S23, the cast sheet is sequentially subjected to crystallization shaping, corona treatment and winding to obtain a PET cast film having a multi-layer film structure.

3. The method for preparing a PET cast film according to claim 1, characterized in that: There are five rollers, and the temperatures of the three rollers between the roller at the starting end and the roller at the end are 45° C., 55° C. and 65° C. respectively.

4. The method for preparing a PET cast film according to claim 2, characterized in that: The step S23 is specifically as follows: According to the preset three-layer film structure, the A layer material, B layer material and C layer material are sequentially fed into the corresponding extruder for plasticization and melting, and then filtered and then extruded into a three-channel die head in the distribution manner of A layer material, B layer material and C layer material from bottom to top. The extrudate is cooled into a casting sheet by a chilled roller.

5. The method for preparing a PET cast film according to claim 2, characterized in that: The step S23 is specifically as follows: According to the preset five-layer membrane structure, the A layer material, B layer material and C layer material are sequentially fed into the corresponding extruder for plasticization and melting, and then filtered and then extruded into a five-channel die head in the distribution manner of A layer material, C layer material, B layer material, C layer material and A layer material from bottom to top. The extrudate is cooled into a casting sheet by a chilled roller.

6. The method for preparing a PET cast film according to claim 2, characterized in that: The A layer material includes PBT and PETG, and the mass ratio of PBT to PETG is 3:7; the B layer material includes PETG; the C layer material includes PBT, APET and SiO2 masterbatch, and the mass ratio of PBT, APET and SiO2 masterbatch is 6.8:3:0.

2.

7. The method for preparing a PET cast film according to claim 2, characterized in that: The extrusion temperature of the extruder corresponding to the A layer material and the B layer material is 220-240°C, the extrusion temperature of the extruder corresponding to the C layer material is 240-260°C, and the temperature of the multi-channel die head is 250°C.

8. The method for preparing a PET cast film according to claim 1, characterized in that: An online thickness measurement is also arranged between the casting and the crystallization shaping.

9. A PET cast film, characterized in that: The PET cast film is prepared by the method for preparing the PET cast film according to any one of claims 1 to 8.

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