JPH0320331B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a deep drawing thermoforming method for propylene polymer laminated sheets that can be deep drawn by vacuum or pressure forming and that provides a product with excellent surface gloss and appearance after forming. Crystalline polyolefin sheets such as polypropylene and polyethylene have excellent mechanical properties, thermal properties, and hygienic properties, so they are used in food trays as substitutes for existing sheets such as polystyrene, acrylonitrile-butadiene-styrene copolymers, and polyvinyl chloride. It has been widely used in food containers, industrial machinery parts, automobile parts, etc. As its applications expanded, technological improvements were made to the composition, and drawing workability during vacuum forming or pressure forming, which was insufficient with conventional sheets made of polyethylene such as polypropylene or polyethylene, was dramatically improved. are doing. The main improvement techniques include, for example, the inventions described in Japanese Patent Application Laid-Open No. 55-108433 and Japanese Patent Application No. 57-25473. The former uses a composition consisting of a specific polyethylene and the same polypropylene, and the latter uses a composition consisting of a specific polypropylene, the same polyethylene, and a specific amount of a styrene polymer. This technology allows polyolefin sheets to be molded over a wider temperature range, and can be drawn more deeply.
Moreover, it has become possible to obtain molded products with less uneven thickness. However, products formed by vacuum or pressure forming using such compositions have the disadvantage of poor gloss. In other words, the raw sheet is contact-cooled with a mirror roll during sheet forming, so the roll surface condition is maintained and a sheet with excellent gloss can be obtained, but it is remelted during the preheating process during vacuum or air pressure forming, and it is difficult to draw. In the subsequent cooling step, it crystallizes in a free surface state, resulting in a decrease in gloss. Therefore, such sheets are inappropriate for application in fields where gloss is required. The purpose of the present invention is to provide a sheet that can be drawn deeply, has no uneven thickness, and can produce a product with excellent gloss, and only a multilayer laminated sheet with layers of specific components satisfies this purpose. This was done after it became clear that That is, in the present invention, at least one surface layer has a melt flow rate of 15 g/10 minutes or less and a propylene content.
75% by weight or more of crystalline propylene polymer 100-95
This is a layer (A layer) consisting of a component of an inorganic nucleating agent or an organic nucleating agent of 0 to 5% by weight, and at least one of the other layers is a crystalline propylene polymer of 5 to 5% by weight.
Ethylene polymer with 85% by weight and density 0.925 or more
Melt flow rate consisting of 95-15% by weight is 5
It is a multilayer resin sheet with two or more layers (layer B) of a composition of g/10 minutes or less, and the layer A has a thickness of 0.5/100 to 45/100 and the layer B has a thickness of 0.5/100 to 45/100 relative to the total thickness of the sheet. For each thickness range from 55/100 to 99.5/100, the deep drawability is 10 seconds or more and the sag is 11 mm according to the deep drawing evaluation method.
The following laminated sheets are deep drawn and thermoformed to form the surface layer.
This is a deep drawing thermoforming method characterized by obtaining a molded product with a gloss of 55% or more according to JIS-Z8741. Such a laminated sheet has excellent gloss and deep drawability, so it can be used in a wide range of applications. Although the specific crystalline propylene polymer (including inorganic filler in some cases) used for the surface layer has extremely poor deep drawing performance in the case of a single-component sheet, It is surprising that the layer structure of the laminated sheet of the present invention does not inhibit the deep drawing performance of other layers. The crystalline propylene polymer constituting the above layer A used in the present invention is JIS-K6758 (230°C, 2.16Kg)
Melt flow rate (MFR) according to 15
g/10 minutes or less, preferably 5 g/10 minutes or less, and a propylene content of 75% by weight or more, which is a homopolymer of propylene or propylene and ethylene or carbon atoms of 4 to 20 (preferably 4 to 12, More preferably, block or random copolymers with α-olefins 4 to 8) are suitable. Comonomers other than α-olefins, such as unsaturated organic acids or derivatives thereof, vinyl esters, and vinyl silanes, may be included within the range that does not impair gloss. At this time, graft copolymerization or random copolymerization is usually adopted. Preferred are copolymers of propylene with a propylene content of 80% by weight or more and ethylene or α-olefins other than propylene, or propylene homopolymers, and more preferred are propylene with a propylene content of 90% by weight or more. and ethylene or an α-olefin other than propylene, a random copolymer of propylene with a propylene content of 85% by weight or more and an α-olefin other than ethylene or propylene, and a homopolymer of propylene. Propylene content is 75
If the amount is less than % by weight, the gloss of the product will be significantly poor. If the MFR of this item exceeds 15g/10 minutes,
In the vacuum forming process, the amount of sagging of the sheet during preheating may become large, and the thickness of the vacuum formed product may become uneven. Moreover, when a recycled product is used for the B layer, it is not preferable because it causes the disadvantage of increasing the MFR of the B layer, which will be described later. Regarding the lower limit of MFR, it can be said that there is actually no limit, as long as it can be formed into a sheet by a molding machine even if it has virtually no fluidity at the time of MFR measurement. This crystalline propylene polymer may be a mixture of two or more of the above. In addition, examples of inorganic nucleating agents that may be added to the above components constituting the A layer include non-organic nucleating agents such as zeolite, amorphous aluminosilicate, calcium carbonate, silica, talc, clay, titanium oxide, and barium sulfate. Fibrous inorganic powders are suitable, and among them, talc with a size of 20 μm or less is effective. In addition, organic nucleating agents include aliphatic and aromatic dicarboxylic acids or their anhydrides, aromatic monocarboxylic acids or their metal salts, amine salts of aliphatic dicarboxylic acids, aluminum salts of aromatic acids,
Diaryl phosphate alkali metal salts are preferred. Among these, aluminum salts of aromatic acids and alkali metal diaryl phosphates are effective. It is preferable to use this inorganic nucleating agent or organic nucleating agent, but when using it, it is added in an amount of 5% by weight or less, more preferably 2% by weight or less based on the total amount with the crystalline propylene polymer. use These additions improve heat resistance, rigidity, scratch resistance,
Although it is expected to provide various effects such as improving dimensional stability and gloss, even if it is added in an amount of 5% by weight or more, no further effects can be expected, and on the contrary, the gloss decreases. Layer A consisting of the above components has excellent gloss and is effective when used in the surface layer of a laminated sheet, so it should be used in the surface layer where appearance is important. Next, the composition constituting the B layer used in the present invention is a blend of a crystalline propylene polymer and an ethylene polymer in specific amounts. The crystalline propylene polymer here includes a propylene homopolymer, propylene and ethylene, or a carbon number of 4 to 4.
20 (preferably 4-12, more preferably 4-8)
Block or random copolymers with α-olefins are preferred. Comonomers other than α-olefins such as unsaturated organic acids or derivatives thereof, vinyl esters, vinyl silanes, etc. may be included as long as they do not inhibit deep drawability. At this time, graft copolymerization or random copolymerization is usually adopted. This crystalline propylene polymer is 2 of the above
Mixtures with more than 10% of seeds may be used, but the propylene content must be 50%
It must be at least 65% by weight, more preferably at least 80% by weight from the viewpoint of rigidity and heat resistance, and JIS-
MFR based on K6758 (230℃, 2.16Kg) is 5
g/10 minutes or less is preferable from the viewpoint of moldability. The ethylene polymer, which is the other component of the composition constituting layer B, is a homopolymer of ethylene or a combination of ethylene and 3 to 20 carbon atoms (preferably 3 to 20 carbon atoms).
~12), more preferably 3~8) copolymers with α-olefins having an ethylene content of 50% by weight or more and a density of 0.925 g/cm ³ or more are suitable.
Ethylene polymers with a density below this range cannot provide good deep drawability. Preferred are ethylene homopolymers and copolymers of ethylene and α-olefin with an ethylene content of 70% by weight or more in terms of rigidity and heat resistance. This ethylene polymer may be a mixture of two or more of the above, but JIS-K6760 (190℃, 2.16Kg)
MFR based on 4g/10 minutes or less, preferably
2 g/10 minutes or less is preferable from the viewpoint of moldability. These two components, crystalline propylene polymer and ethylene polymer, are mixed in a proportion of 5 to 85% by weight of the former and 5 to 85% by weight of the latter.
Among the compositions containing 95 to 15% by weight, MFR [here, based on JIS-K6758 (230℃, 2.16Kg)]
5 g/10 minutes or less, preferably 3 g/10 minutes or less, is suitable as a constituent of layer B. In this composition, if the crystalline propylene polymer is less than 5% by weight, or the ethylene polymer is more than 95% by weight, the amount of sheet sagging during the preheating process during vacuum forming will be large, and in commercial machines, the amount of sagging with the lower heater will increase. In order to avoid contact, there is a disadvantage that the molding time is substantially shortened.On the other hand, if the crystalline propylene polymer is more than 85% by weight, or the ethylene polymer is less than 15% by weight, the deep drawability will be greatly impaired. However, this is not preferable because it causes uneven wall thickness of the molded product. In addition, if the MFR of this composition is greater than 5 g/10 minutes, the sheet will sag excessively during the preheating process during vacuum or pressure forming, which is undesirable as wrinkles and uneven wall thickness will occur in the product. . Regarding the lower limit of MFR, even if the material has virtually no fluidity at the time of MFR measurement, it may be formed into a sheet by a molding machine, and it can be said that there is actually no limit. Layer B composed of such a composition has excellent external deep drawability.
~95 parts by weight, preferably 80 to 90 parts by weight, and 60 to 5 parts by weight of an inorganic filler that can be used as a component of the layer A,
When a composition containing preferably 20 to 10 parts by weight is used in layer B, a sheet is obtained that is not only deep drawable but also has heat resistance, rigidity, and dimensional stability. is more preferable. In this case, if more than 60 parts by weight of the inorganic filler is blended, the deep drawability will deteriorate, while if it is less than 5 parts by weight, the blending effect will be insufficient. In addition, as for the type of inorganic filler, in addition to those mentioned above in the inorganic nucleating agent, fibrous materials such as glass fiber and potassium titanate can also be used, but in particular, talc, calcium carbonate, etc. is preferable in terms of moldability, rigidity, impact resistance, etc. When the constituent of layer A is a composition and B
The composition constituting the layer is prepared by a conventional kneading method, for example, using a kneading machine such as an extruder, roll, or Banbury. Usually, the compound is kneaded in an extruder or the like to form a pellet-like compound, which is then processed into a sheet, but it is also possible to directly form a sheet after dry-blending the various mixed components. At this time, each component constituting the A and B layers,
Components other than these components, such as antioxidants, ultraviolet absorbers, antistatic agents, lubricants, dispersants, clarifying agents, colorants, corrosion inhibitors, etc., may be added as appropriate depending on the purpose. Furthermore, the laminated sheet is made by a general lamination method. The multilayer sheet of the present invention can be manufactured by a commonly used lamination method. For example, a coextrusion method using a multi-manifold die or feed block; layer A is produced in advance into a film or sheet using a T-die or inflation die, and layer B or B is formed on the film or sheet. A method of extruding and laminating a laminate having at least one layer into a sheet in a molten state; B
A method of manufacturing a laminated sheet having at least one layer or B layer in advance using a T-die, and then extruding and laminating layer A in a molten state on top of it; lamination having at least one layer B or B layer. The sheet and the layer A are manufactured separately in advance, and the two sheets are pasted together via an adhesive layer such as an adhesive or an adhesive molten resin. In this multilayer sheet, at least one surface layer must be layer A, and at least one other layer must be layer B, and the thickness of the entire sheet must be A layer.
The layer is 0.5/100~45/100, preferably 1/100~30/100
and layer B is 55/100 to 99.5/100, preferably 70/1
Must be in the range of 00 to 99/100. The multilayer sheet of the present invention has two important layers: a glossy layer and a layer having a deep drawing function, and the thickness ratio of each layer to the total thickness of the sheet influences the gloss and drawing performance. If the thickness of the A layer is smaller than the above range, the gloss will be significantly reduced, and if it is larger, the drawing performance will be reduced. Furthermore, if the B layer is smaller than the above range, the drawing performance will be reduced, and if it is larger than the above range, the necessary thickness of the glossy layer cannot be ensured. Among the laminated sheets obtained in this way, the deep drawability according to the deep drawing evaluation method was 10 seconds or more and the amount of sagging was
Only those below 11 mm can be applied to the present invention. Here, the method for measuring deep drawability and sagging amount using the deep drawing evaluation method is as follows. (1) Deep drawability: A single-layer or multi-layer sheet with a thickness of approximately 1.5 mm is sandwiched between two plates (250 mm x 250 mm x 3 mm) with a 150 mm diameter hole in the center, and placed horizontally in an insulated box. Set to . At this time, in the case of a multilayer sheet, layer A is the top surface. Next, in order to heat the sheet evenly, set the temperature to 450
Slide the heater heated to ℃ to a height of 15 cm above the seat. The heated sheet first expands toward the heater. Thereafter, as the temperature increases uniformly in the thickness direction of the sheet, the sheet becomes horizontal again, and from then on, the sheet begins to sag due to its own weight. Here, a large number of sheets are tested for each item, but based on the time when the first sheet becomes horizontal again, there are ±5 seconds before and after that, and ±10 seconds.
Remove the heater at intervals of ±15 seconds, push in a felt-wrapped plug with a tip radius of 40 mm and a diameter of 80 mm at a speed of 240 mm/second and pressure.
Push to 150mm at 1.0Kg/cm ² . The aperture ratio at that time is 1.0. After cooling, remove the push-in plug and pass light through the molded product or observe thickness unevenness with a dial gauge. Using the above method, we observed the drawing ratio and wall thickness unevenness of the molded product at each preheating time, and found that the drawing ratio was 1.0.
The preheating time at which a molded product with an even thickness can be obtained is measured. (2) Amount of sagging: Using a device for evaluating deep drawability, measure the amount by which the center of the sheet sag after 4 minutes of preheating. It can be said that the longer this preheating time, the wider the moldable temperature range, and the sheet with better moldability. Thermoforming includes vacuum forming, pressure forming, solid phase pressure forming, solid phase press forming, stamping molding, and the like. The molded product obtained by deep drawing thermoforming has a surface layer that is JIS-Z8741 (the angle is 60 degrees -
60 degrees) with a gloss of 55% or more. Next, examples will be shown, and each evaluation method is as follows. (1) Deep drawability: Based on the measurement method above. (2) Gloss: Select the one with the most uniform wall thickness distribution from among the U-shaped molded products whose deep drawability was evaluated, cut off the top 1/3, and measure the gloss according to the measurement method above. Measure. If there are many molded products with uniform wall thickness distribution, take the average of them. (3) Sagging amount: Based on the above measurement method. (4) Elastic modulus: Three-point bending modulus according to JIS-K7203. Example 1 Resin used for the glossy layer: A crystalline propylene homopolymer with an MFR of 2.0 g/10 minutes and a residual amount of 99% by weight after extraction with boiling heptane was used. Resin used for deep drawing layer: Ethylene content 5% by weight, MFR 0.5g/10 minutes, boiling heptane extraction remaining amount 98
50% by weight crystalline propylene-ethylene block copolymer, density 0.950g/cm ³ , MFR 0.6
50% by weight of polyethylene of g/10 min was kneaded into pellets using an extruder. The MFR of this thing is 0.40
g/10 minutes. Manufacture of sheet: The resin for the deep drawing layer is supplied to a two-layer multi-manifold die with a width of 700 mm at 200 to 270 °C using an extruder with a diameter of 90 mm, and the resin for the gloss layer is supplied to a 2-layer multi-manifold die with a width of 700 mm using an extruder with a diameter of 40 mm. The same die was fed at ~270°C. The temperature of the die was 230-240°C.
The molten sheet extruded from the die was sequentially cooled and solidified using three rolls each having a width of 700 mm. The temperature of the rolls is 80℃, 95℃, 100℃ starting from the roll closest to the die.
The rotation speed of the roll was 1.5 m/min. The total sheet thickness was 1.6 mm, the gloss layer was 0.25 mm, and the deep drawing layer was 1.35 mm. The evaluation of the sheets is shown in Table 1. Example 2 Ethylene content 3% by weight in glossy layer, MFR 0.5g/
The test was conducted in the same manner as in Example 1, except that a crystalline propylene-ethylene block copolymer with a residual amount of 99% by weight after extraction with boiling heptane for 10 minutes was used. Example 3 Ethylene content in glossy layer: 8% by weight, MFR: 1.2g/
The test was carried out in the same manner as in Example 1, except that a crystalline propylene-ethylene block copolymer having a residual amount of 98% by weight after extraction with boiling heptane for 10 minutes was used. Example 4 Ethylene content 2% by weight in glossy layer, MFR 1.6g/
The test was conducted in the same manner as in Example 1, except that a 10-minute crystalline propylene-ethylene random copolymer was used. Example 5 Butene-1 content 18% by weight in glossy layer, MFR 0.6
The test was carried out in the same manner as in Example 1 except that a crystalline propylene-butene-1 random copolymer having a ratio of 1 g/10 min was used. Comparative example 1 Ethylene content 27% by weight in glossy layer, MFR 0.5g/
The test was carried out in the same manner as in Example 1, except that a crystalline propylene-ethylene block copolymer having a residual amount of 97% by weight after extraction with boiling heptane for 10 minutes was used. Comparative Example 2 Butene-1 content 27% by weight in glossy layer, MFR2.0
The test was carried out in the same manner as in Example 1, except that a crystalline propylene-butene-1 random copolymer with a boiling heptane extraction rate of 60% by weight was used. Comparative Example 3 A single layer manifold die was attached to the 90 mm diameter extruder used in Example 1, and the deep drawn layer resin pellets used in Example 1 were extruded to obtain a sheet with a thickness of 1.6 mm. The molding conditions were the same as in Example 1. Comparative Example 4 In Comparative Example 3, a sheet was prepared using only the crystalline propylene-ethylene block copolymer used as one component of the resin for the deep drawing layer in Example 1. Examples 6 to 8 and Comparative Examples 5 and 6 Tests were conducted in the same manner as in Example 1, except that the blending ratio of the two components of the deep drawing layer resin was varied as shown in Table 1. Example 9 and Comparative Example 7 In Example 1, the composition used for the deep drawing layer was
Example 1 except that each resin component used in the deep drawing layer was changed as shown in Table 1 in order to change the MFR.
Tested in the same manner. Example 10 and Comparative Examples 8 and 9 Tests were conducted in the same manner as in Example 1, except that the thickness composition ratio of the glossy layer and the deep drawing layer was changed as shown in Table 1. Example 11 and Comparative Example 10 Tests were conducted in the same manner as in Example 1, except that crystalline propylene homopolymers with MFRs changed as shown in Table 1 were used for the glossy layer. These results are shown in Table 1.

【table】

[Table] Examples 12, 13 In Example 1, the resin used for the glossy layer was pelletized by adding 0.3% by weight of talc or aluminum salt of pt-butylbenzoic acid with an average particle size of 4μ, and then pelletized. Example 1 except that used in
Tested in the same manner. Comparative Example 11 A test was conducted in the same manner as in Example 12, except that talc was changed to 8% by weight. Examples 14, 15 and Comparative Example 12 Examples except that in Example 1, the resin used for the deep drawing layer was added with talc or calcium carbonate in the proportions shown in Table 2. The test was conducted in the same manner as in 1. As a control, the flexural modulus of the sheet of Example 1 was also measured. These results are shown in Table 2.

【table】

【table】 [Brief explanation of the drawing]

Figures 1 and 2 are side views of two-layer or three-layer sheets of the present invention.

Claims (1)

[Claims] 1. At least one surface layer has a melt flow rate of 15
g/10 minutes or less of crystalline propylene polymer with a propylene content of 75% or more by weight and 0 to 95% by weight.
A layer (A layer) consisting of 5% by weight of an inorganic nucleating agent or an organic nucleating agent, and at least one of the other layers contains 5 to 85% by weight of a crystalline propylene polymer and a density of 0.925 g/cm ³ or more. A layer (B layer) of a composition consisting of 95 to 15% by weight of ethylene polymer and having a melt flow rate of 5 g/10 minutes or less, and the above A layer is 0.5/100 to 45/100 of the total thickness of the sheet. and the above B layer has a thickness range of 55/100 to 99.5/100,
A laminated sheet with a deep drawability of 10 seconds or more and a sagging amount of 11 mm or less according to a deep drawing evaluation method is deep drawn and thermoformed to obtain a molded product whose surface layer has a gloss of 55% or more according to JIS-Z8741. deep drawing thermoforming method. 2 The B layer is a resin component of 5 to 85% by weight of crystalline propylene polymer and 95 to 15% by weight of ethylene polymer.
A deep drawing thermoforming method characterized in that the composition is a composition containing 40 to 95 parts by weight of an inorganic filler and 60 to 5 parts by weight of an inorganic filler.