JPH047380B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a polyethylene composition for obtaining a polyethylene foam with excellent moldability. [Prior art] Conventionally, polyethylene compositions for foams have been disclosed in Japanese Patent Application Laid-Open No. 56-34732 and Japanese Patent Application Laid-open No. 57-34732.
Publication No. 202325, Publication No. 57-202326, Publication No. 57-
Those described in Publication No. 202327 are known. The above items are related to this applicant. [Disadvantages of the prior art] However, in all of the above known polyethylene compositions for foams, the molecular structure and thermal properties of the polyethylene (hereinafter abbreviated as PE) in the composition do not meet the appropriate range. Therefore, it had the disadvantage of poor moldability when made into a foam. [Object of the Invention] The object of the present invention is to provide a method for producing a PE foam that does not have the above drawbacks, that is, has excellent moldability. [Structure of the Invention] In order to achieve the above object, the present invention provides a method for producing a polyethylene foam in which a polyethylene resin composition is extruded, crosslinked, and then foamed to obtain a foam. , ethylene component A and at least one component B selected from 1-butene, 1-pentene, 1-hexene, 3,3-dimethyl-1-butene, 4-methyl-1-pentene, and 1-octene. Abstract: A method for producing a polyethylene foam characterized by using a polyethylene copolymer comprising Component B in a copolymerization ratio of 1 to 10 mol% and having the following properties. shall be. Absorbance ratio by infrared absorption spectrum (IR) a = [A ₁₃₈₀ / (A ₁₃₈₀ + A ₁₃₇₀ + A ₁₃₅₅ )] × 100
(%) is 5 to 50%, and b = [A ₇₃₀ / (A ₇₃₀ + A ₇₂₀ )] x 100 (%) is 40 to 55%. Here, A ₁₃₈₀ is 1380cm ^-1 ,
A ₁₃₇₀ is 1370cm ^-1 , A ₁₃₅₅ is 1355cm ^-1 , A ₇₃₀
represents the absorbance at 730 cm ^-1 and A ₇₂₀ represents the absorbance at 720 cm ^-1 . Melting point (T _n ), crystallization temperature (T _nc ), and isothermal crystallization temperature (t1/2) measured by differential scanning calorimeter The main peak of T _n is 110 to 135°C, and the main peak of T _nc is 85 to 110°C. , t1/2 at 115°C is 1 minute to 10 minutes. Melt index (MI) 1-50g/10 minutes. Melt viscosity (μ _a ) 500-15000 poise. Brabender Plast Equilibrium Torque 200~2500
g・m. As seen above, the properties of the polyethylene resin composition used in the production method of the present invention are defined as described above. That is, in the absorbance ratio according to the infrared absorption spectrum, 5%≦a≦50% and 40%≦b≦55%
It is necessary that both are satisfied. a,
If either or both of b is out of the above range, crosslinking by electron beams and crosslinking by peroxide becomes difficult to control, making it impossible to obtain the desired foam. In addition, 1380cm ^-1 , 1370cm
The characteristic absorption bands of ^-1 , 1355 cm ^-1 and 730 cm ^-1 and 720 cm ^-1 are assigned as follows based on their respective molecular structures. 1380cm ^-1 ; Due to PE-based side chains and terminal methyl groups. 1370cm ^-1 ; Due to the crystalline region of PE main chain methylene. 1355cm ^-1 ; Due to the amorphous region of PE main chain methylene. 730cm ^-1 ; Due to the crystalline region of 4 or more PE-based methylene chains (including main chains and branched chains). 720cm ^-1 ; Due to the amorphous region of PE-based methylene chains. In this invention, the melting point (hereinafter abbreviated as _Tn ), crystallization temperature (hereinafter abbreviated as _Tnc ), and isothermal crystallization rate (hereinafter abbreviated as t1/2) are measured using a differential scanning calorimeter (hereinafter abbreviated as DSC). 110℃≦T _n ≦135℃ (preferably 115℃≦T _n ≦125℃) 85℃≦T _nc ≦110℃ (preferably 88℃≦T _nc ≦105 °C) 1 minute≦t1/2≦10 minutes (preferably 1 minute 30 seconds≦t1/2≦6 minutes). If T _n is less than 110°C, dimensional stability will be affected, and if it exceeds 135°C, extrusion processability will deteriorate. When T _nc is less than 85℃,
Deformation occurs due to the elapsed time after the foam sheet is created, and if the temperature exceeds 110°C, the processing characteristics during foam sheet processing will deteriorate and the creation of the foam sheet will be adversely affected. If t1/2 is less than 1 minute, the foam sheet will be highly deformed and distorted unless a special cooling method is used, and if it exceeds 10 minutes, the sheet will gradually deform over time during sheet molding, making it difficult to It is difficult to use as a foam sheet. In this invention, MI needs to be in the range of 1 to 50 g/10 minutes, preferably 2.0 to 50 g/10 minutes.
It should be within the range of 30g/10 minutes. MI is 1
If it is less than g/10 minutes, the required power load during extrusion molding becomes excessive, which is not preferable for producing a suitable foam sheet. On the other hand, if it exceeds 50g/10 minutes,
Although it has a positive effect on sheet forming, the gas retention force during foaming becomes weak, making it difficult to obtain a product with a high foaming ratio. In this invention, the melt viscosity (μ _a ) needs to be 500 to 15,000 poise, preferably 2,000 to 12,000 poise. If the melt viscosity is less than 500 poise, drafts due to the sheet's own weight will be generated during sheet molding, resulting in large internal distortions, making it difficult to obtain a stable foam.
On the other hand, when it exceeds 15,000 poise, the conditions during extrusion molding become very narrow and it is difficult to obtain stable extrusion conditions. In this invention, the equilibrium torque value of the Brabender plastograph must be 200 to 2500 g.m, preferably 400 to 1800 g.m. If the equilibrium torque value of the Brabender Plastograph is less than 200g/m, stable extrusion is often not possible unless special equipment or conditions are set during extrusion.
If it exceeds g/m, the driving load on the extruder during extrusion molding becomes excessive, or the extrusion temperature becomes difficult to control due to the generation of shear heat, resulting in decomposition of the foaming agent, etc., which may result in good foaming. I can't get a sheet for this. Next, a method for producing the PE copolymer used in this invention will be explained. First, using the known high-pressure method, medium-low pressure method, and low-pressure method.
PE-based copolymers are manufactured using PE-based copolymer manufacturing technology. In this case, in order to satisfy the purpose of this invention, the above-mentioned IR, T _n , T _nc , t1/2, MI, melt viscosity, and Brabenderplast equilibrium torque must be satisfied, and for that purpose, high pressure So-called linear low-density PE (L-LDPE), which is generally produced by a medium-low pressure method, is preferable to low-density PE (LDPE) produced by the method or high-density PE (HDPE) produced by the low-pressure method. Also desirable is so-called medium density PE (MDPE). For this reason, in the present invention, for the ethylene component A, 1-butene, 1-pentene, 1
-hexene, 3,3-dimethyl-1-butene, 4-
At least one component B selected from methyl-1-pentene and 1-octene is copolymerized. The copolymerization ratio of component B must be 10 mol% or less and 1 mol% or more. If this range is set, the above IR, T _n , T _nc , t
It becomes easy to set 1/2, MI, melt viscosity, and Brabender torque within specific ranges. The polymerization method can be carried out by various methods such as slurry polymerization, gas phase polymerization, and high-temperature solution polymerization, but the degree of polymerization and branching can be controlled by appropriately selecting catalysts and polymerization conditions to achieve a predetermined level.
It can be IR, T _n , T _nc , MI, t1/2, melt viscosity, Brabender torque. However, the manufacturing method is not particularly limited. Specific examples of PE-based copolymers include Sumikasen-L FA201-0 and Sumikasen-L manufactured by Sumitomo Chemical Co., Ltd.
An example is FA202-0. It should be noted that less than 10% by weight of other polymers may be mixed with the above-mentioned PE-based copolymer as long as the object of the present invention is not impaired. Next, to the above PE copolymer, 100 parts by weight of the above PE copolymer (hereinafter referred to as 5 to 20 parts per 100 parts of the above PE-based copolymer;
Then, optional amounts of auxiliary agents, flame retardants, plasticizers, antistatic agents, inorganic substances, low-viscosity organic polymers such as wax, lubricants, pigment colorants, ultraviolet inhibitors, etc. are added to form a PE-based composition for foam. To make a foam from this composition, it is extruded using a known method, crosslinked using an ionizing radiation method or heating method, foamed using a pressurizing method, pressurization/decompression method, or heating method, and molded into a sheet or any shape. do. [Measurement method and evaluation criteria for characteristics] The measurement method and evaluation criteria for characteristics in this invention are as follows:
It is as follows. IR device: Hitachi, Ltd. EPI-G3 type Conditions: Scanning speed 60 cm ^-1 / min (4000 to 400 cm ^-1 )
The metering section is 30cm ^-1 /min (chart speed 60cm ^-1 /
(twice the minute and hour). Sample preparation: 5g of sample was placed on an 80μ biaxially stretched polyester film and heated and pressed at 160°C.
50±3μ and rapidly cooled to below 20℃.
Use as a sample. Evaluation criteria: Calculated as follows from charts measured by the above measurement method. () How to find 1380~1355cm ^-1 1400~1390cm and 1345~1335 on the chart
The straight line connecting around cm ^-1 is taken as the baseline,
Find the absorbance of each wavenumber of 1380, 1370, and 1355. () How to find 730cm ^-1 to 720cm ^-1 As a straight baseline passing through 850 to 900cm ^-1 and 700 to 650cm ^-1 , find the absorbance at each wave number of 730cm ^-1 and 720cm ^-1 . () () The absorbance obtained in () is the density,
The value corrected by the film thickness is used as the value for calculating the absorbance ratio. T _n , T _nc , t1/2 by DSC Equipment: DSC-2 model manufactured by Perkin Elma Conditions: Measurement of T _n , T _nc . Take 5 mg of the sample into the specified aluminum holder. At a heating rate of 20℃/min
Raise the temperature to 280°C, hold at 280°C for 5 minutes, and then lower the temperature at 20°C/min. chart speed 40
mm/min. Evaluation criteria: The largest peak value on the temperature rising side in the spectrum of the DSC chart.
Let T _n . The start of melting is defined as the point at which a change appears in the temperature increase curve, and the end point is defined as the end point of the highest point. T _nc is expressed by the largest peak value in the temperature drop curve. For t1/2, raise the temperature of the sample to 280℃ and hold it for 5 minutes.
Rapidly cool to ℃, take a curve, and express it as 1/2 of the difference between the crystallization start time and crystallization end time. MI device: Melt Indexer MX manufactured by Toyo Seiki Co., Ltd.
-101-B type. Conditions: Measured using a method based on JIS K6760-1981. Evaluation criteria: This is a value measured according to JIS K6760-1981, and it is determined whether it is within the above range. Melt viscosity equipment; height flow tester manufactured by Shimadzu Corporation
Type 301. Conditions: Temperature conditions are 130℃, 150℃, 170℃, 190℃
4 points. The shear rate can be arbitrary, but
Due to viscosity regulations, it is set to 1001/sec. The nozzle is 0.5φ x 1mm, and the sample weighs 5g. The heating time is 5 minutes after the sample is added, and the measurement is started after the heating time has elapsed. Evaluation criteria: After plotting the measured values at each temperature on a temperature-viscosity relationship diagram and observing the viscosity change,
Determine whether the viscosity at 190°C is within the above range. Brabender Plast Balance Torque Equipment: Labo Plast Mill Roller Mixer manufactured by Toyo Seiki Co., Ltd. Conditions: Temperature: 165℃ Sample: 35g Blade rotation speed
100rpm load 2Kg. Evaluation criteria: The value that has reached equilibrium in the torque curve of the measured data is defined as an equilibrium torque value, and it is determined whether it is within the above range. Formability parameters S, L and SL Apparatus: Shorter type tensile tester manufactured by Kobunshi Keiki Seisakusho Co., Ltd. Conditions: Sample No. 3 dumbbell shape, tensile speed 50mm/
Minutes. S: Value obtained by converting the strength of the sample at breakage per 1 cm. L: Percentage value of elongation when the sample breaks with respect to the sample length. Evaluation criteria: Good moldability is when S, L and SL obtained by the above method simultaneously satisfy the following ranges. S≧2.0Kg/cm ² L≧200% SL≧400Kg/cm ² ·% Preferably, the following conditions are satisfied: S≧2.7Kg/cm ² L≧220% SL≧594Kg/cm ² ·%. [Examples, Comparative Examples] Examples 1 to 3 and Comparative Examples 1 to 5 are as follows. Using PE as shown in Table 1, its PE100
blowing agent (azodicarbonamide) per 10 parts
1 part, add 4 parts of crosslinking aid (divinylbenzene),
After mixing both, one part of M1200 low-density PE (Sumikasen G808, manufactured by Sumitomo Chemical Co., Ltd.) was added as a foam stabilizer to prepare a composition. The composition was introduced into an extruder and extruded at 150°C. In addition, 6 Mrad of radiation was applied using an electron beam accelerator (IR-
Electron beam irradiation was performed in step 2). Next, it was heated and foamed in a hot air oven at 230°C. The moldability of the obtained foam was evaluated, and the comprehensive judgment results are listed in Table 1.

【table】

〔Effect of the invention〕

In the method for producing a foam according to the present invention, the resin of the PE-based composition used as a raw material is made by copolymerizing component A with a specific amount of component B, and has a specific IR, specific T _n , T _nc , t1/ 2 Specific MI, specific melt viscosity,
Since it satisfies the specific Brabender plastic equilibrium torque at the same time, the foam obtained therefrom has the advantage of excellent moldability. Formability here is synonymous with toughness as a foam, which can be parameterized by the foam's breaking strength S, breaking elongation L, and their product SL;
The larger the L, SL value, the tougher it is, i.e.
It can be evaluated that the moldability is good. Another advantage is that it has excellent thermal dimensional stability. [Applications] Because the foam obtained from this invention has the above-mentioned effects, it can be used in automobile applications such as front panels, door panels, ceilings, etc., where it is deep-drawn using various forming methods, think tanks, and heat-insulating ceiling materials. Suitable for deep drawing in etc. and acute angle folded plates.
In particular, it is suitable for industrial fields such as the automobile field, which has a high degree of deep drawability.

Claims (1)

[Scope of Claims] 1. A method for producing a polyethylene foam in which a polyethylene resin composition is extruded, crosslinked, and then foamed to obtain a foam, wherein the polyethylene resin contains an ethylene component A and 1- Butene, 1-pentene, 1-hexene, 3.3-dimethyl-1-butene, 4-methyl-1-pentene, 1
- Use a polyethylene copolymer that is composed of at least one component B selected from octene, has a copolymerization ratio of component B of 1 to 10 mol%, and has the following properties: A method for producing a polyethylene foam, characterized by: Absorbance ratio by infrared absorption spectrum a = [A ₁₃₈₀ / (A ₁₃₈₀ + A ₁₃₇₀ + A ₁₃₅₅ )] × 100
(%) is 5 to 50%, and b = [A ₇₃₀ / (A ₇₃₀ + A ₇₂₀ )] x 100 (%) is 40 to 55%. Here, A ₁₃₈₀ is 1380cm ^-1 ,
A ₁₃₇₀ is 1370cm ^-1 , A ₁₃₅₅ is 1355cm ^-1 , A ₇₃₀
represents the absorbance at 730 cm ^-1 and A ₇₂₀ represents the absorbance at 720 cm ^-1 . Melting point (T _n ), crystallization temperature (T _nc ), and isothermal crystallization temperature (t1/2) measured by differential scanning calorimeter The main peak of T _n is 110 to 135°C, and the main peak of T _nc is 85 to 110°C. , t1/2 at 115°C is 1 minute to 10 minutes. Melt index (MI) 1-50g/10 minutes. Melt viscosity (μ _a ) 500-15000 poise. Brabender Plast equilibrium torque 200-2500g・m.