JP2012166407A - Method of manufacturing polyolefin-based resin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyolefin-based resin sheet having excellent heat resistance and dimensional stability by improving the crystallinity of the polyolefin-based resin sheet without carrying out a high-speed and high-pressure rolling elongation.SOLUTION: The method of manufacturing polyolefin-based resin sheet includes: a melting step of melting a polyolefin-based resin to make a molten polyolefin-based resin; a holding step of holding, for a prescribed time, the polyolefin-based resin after melting step, at a temperature above the glass transition temperature (Tg) and below the melting point (Tm); and a pressurizing step of pressuring the polyolefin based resin after the holding step within the temperature.

Description

  The present invention relates to a method for producing a polyolefin resin sheet. More specifically, the present invention relates to a production method capable of providing a polyolefin resin sheet having excellent heat resistance.

  So-called general-purpose plastics are extremely easy to process, are lighter than materials such as metal, and are inexpensive, so they are used in daily products such as sheets, bags, various containers, and packaging, as well as industrial products such as automobiles and electrical machinery. Widely used as materials for miscellaneous goods. Typical examples of general-purpose plastics include polyethylene, polypropylene, polyvinyl chloride, polystyrene, and the like, but these resins do not have sufficient mechanical strength and lack heat resistance. Further, even when transparency is required as a material for industrial products, in most cases, the requirement is not satisfied. For example, even the polypropylene, which is said to have relatively high heat resistance among the above-mentioned general-purpose plastics, has a softening temperature of about 130 ° C. at most and is not sufficient for use as an industrial product. As described above, the general-purpose plastic has a problem that its use is limited because it does not have sufficient transparency and mechanical properties required for various industrial products.

  Therefore, it has been proposed to improve functionality by greatly improving various physical properties required for industrial products such as heat resistance, mechanical properties and transparency of general-purpose plastics, and to use them as substitute materials for engineer plastics. For example, Patent Document 1 discloses a method for producing a polypropylene crystal by crushing a rod-shaped polypropylene at a crystallization temperature at high speed. Patent Document 2 describes a highly crystalline polymer crystal.

  However, the method for producing a polypropylene crystal described in Patent Document 1 varies depending on the strain rate in the rod, the uniformity of the polypropylene crystal is low, and a large amount of high-molecular-weight polypropylene crystal is produced. And it has the problem that it cannot manufacture continuously. In addition, since the polymer crystal described in Patent Document 2 contains a nucleating agent, the difference between the polymer melt and the crystallization temperature is reduced, and the molding conditions of the polymer crystal are reduced.

  Therefore, in order to align the molecular chain of the crystalline resin in a large amount and with high orientation, a method for producing a resin film that is rolled at a specific temperature so as to deform the crystalline resin melt at a large strain rate is proposed. (Patent Document 3). In addition, a polymer sheet is disclosed which is produced by sandwiching a supercooled polymer melt between a pair of sandwiching rolls and crystallizing by stretching at a stretching strain rate equal to or higher than the critical stretching strain rate ( Patent Document 4).

International Publication No. 2008/108251 JP 2008-248039 A International Publication No. 2010/084766 International Publication No. 2010/084750

  However, the crystalline resin film manufacturing method disclosed in Patent Documents 3 and 4 or the polymer sheet manufacturing method cannot be achieved with a normal compressor because high crystallization cannot be achieved unless pressure stretching is performed at a critical elongation strain rate or higher. It was not possible to do so, and further improvement was demanded.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a polyolefin resin sheet that improves the crystallinity of the polyolefin resin sheet and is excellent in heat resistance and dimensional stability. There is.

  The present inventors have found that a polyolefin resin excellent in heat resistance and dimensional stability can be produced by holding a molten polyolefin resin for a predetermined time at a predetermined temperature before pressure treatment. The present invention has been completed. Specifically, the present invention specifically provides the following.

(1) a melting step of melting a polyolefin resin to form a molten polyolefin resin;
A holding step of holding the polyolefin resin after the melting step for a predetermined time within a temperature between the glass transition temperature (Tg) and the melting point (Tm);
And a pressurizing step of pressurizing the polyolefin resin after the holding step within the above temperature.

  (2) The polyolefin resin according to (1), wherein the holding step includes lowering the temperature to the temperature T1 within the temperature, raising the temperature to the temperature T2 within the temperature, and then holding the temperature at the temperature T2. Sheet manufacturing method.

  (3) The method for producing a polyolefin resin sheet according to (1) or (2), further comprising a step of performing an annealing treatment after the pressing step.

  (4) The method for producing a polyolefin resin sheet according to any one of (1) to (3), wherein the polyolefin resin is a polypropylene resin.

  (5) A polyolefin resin sheet obtained by the polyolefin resin sheet manufacturing method according to any one of (1) to (4), wherein the longitudinal dimension change rate and the horizontal dimension are measured by a heating dimensional change measurement method according to JIS K7133. A polyolefin-based resin sheet having a change rate of 1.0% or less.

  According to the method for producing a polyolefin-based resin sheet of the present invention, a polyolefin-based resin sheet with improved crystallinity and excellent heat resistance and dimensional stability is produced under relaxed conditions instead of high-speed and high-pressure conditions. A method can be provided.

It is the figure which showed the temperature change (Examples 1-4) in the manufacturing process of a polypropylene resin sheet. It is a graph which shows the crystallinity degree measurement result (Example 1) of a polypropylene resin sheet. It is a graph which shows the crystallinity measurement result (Example 2) of a polypropylene resin sheet. It is a graph which shows the crystallinity measurement result (Example 3) of a polypropylene resin sheet. It is a graph which shows the crystallinity degree measurement result (Example 4) of a polypropylene resin sheet. It is a graph which shows the crystallinity measurement result (comparative example 1) of a polypropylene resin sheet. It is a graph which shows the crystallinity degree measurement result (comparative example 2) of a polypropylene resin sheet. It is a graph which shows the crystallinity degree measurement result (Example 5) of a polypropylene resin sheet. It is a graph which shows the crystallinity degree measurement result (comparative example 3) of a polypropylene resin sheet.

<Production method of polyolefin resin>
The method for producing a polyolefin-based resin according to the present invention includes a melting step in which a polyolefin-based resin is melted to obtain a molten polyolefin-based resin, and the polyolefin-based resin after the melting step has a melting point (Tm) exceeding the glass transition temperature (Tg). A holding step of holding for a predetermined time within a temperature of less than a) and a pressing step of pressing the polyolefin resin after the holding step within the temperature. Hereinafter, each step will be described. In the method for producing a polyolefin resin of the present invention, the polyolefin resin sheet is a concept including a film as well as a sheet.

(Melting process)
In the method for producing a polyolefin resin sheet of the present invention, a polyolefin resin as a raw material is melted to obtain a molten polyolefin resin. In order to make the polyolefin resin into a molten polyolefin resin, heating is performed at a temperature equal to or higher than the melting point of the polyolefin resin to be used.

  For example, when the polyolefin resin is a polypropylene resin, the polyolefin resin is melted by supplying the pellet-shaped polyolefin resin into the top plate of the compressor and heating the top plate. It can be a resin. The temperature of the molten polyolefin resin is not particularly limited as long as it can maintain uniform fluidity, but it is preferably 30 to 50 ° C. higher than the melting point of the polyolefin resin to be used. For example, when a polypropylene resin is used as the polyolefin resin, it can be set to 180 to 210 ° C., which is 30 to 50 ° C. higher than the melting point of crystalline polypropylene, which is about 160 ° C.

  The polyolefin resin used for the molten polyolefin resin includes a so-called polyolefin resin, and is preferably a crystalline polyolefin. Specifically, polyethylene, isotactic polypropylene, syndiotactic polypropylene, poly 1-butene, poly 4 methyl 1-pentene, 1-hexene, or a block copolymer of monomers constituting these polymers and other monomers Or a random copolymer can be illustrated.

(Holding process)
Next, in the method for producing a polyolefin resin sheet of the present invention, the polyolefin resin after the melting step is held for a predetermined time within a temperature between the glass transition temperature (Tg) and the melting point (Tm). Process. In the conventional method for producing a polyolefin resin sheet or the like, the molten crystalline resin is discharged from a die or the like, and immediately after that is used as a resin sheet or film, but the production of the polyolefin resin sheet of the present invention In the method, the polyolefin resin is provided by providing the temperature holding step and holding the polyolefin resin after the melting step for a predetermined time within a temperature between the glass transition temperature (Tg) and the melting point (Tm). It is presumed that this contributes to further improving the crystallinity of the polyolefin resin by adjusting the orientation of the molecular chain.

  Since the temperature of the molten polyolefin resin after the step of forming the molten polyolefin resin is 30 to 50 ° C. higher than the melting point of the polyolefin resin, in the temperature holding step, after the melting step The polyolefin-based resin is lowered to a temperature within the temperature between the glass transition temperature (Tg) and the melting point (Tm).

  If the temperature within the temperature between the glass transition temperature (Tg) and less than the melting point (Tm) is higher than the glass transition temperature (Tg) of the polyolefin resin used and less than the melting point (Tm), the polyolefin Although it can be appropriately set according to the physical properties of the resin, it is preferably a glass transition temperature (Tg) of the polyolefin resin plus 5 ° C. or more and a melting point (Tm) of minus 5 ° C., more preferably It is preferable that the glass transition temperature (Tg) plus 10 ° C. or higher and the melting point (Tm). If it is in the said range, since the orientation of the molecular chain which comprises polyolefin resin can be improved, it is preferable.

  For example, when a polypropylene resin is used as the polyolefin resin, the melting point of the crystalline polypropylene (isotactic polypropylene) resin is about 160 ° C., so the temperature should be set in the range of 125 to 150 ° C. Can do. In addition, holding | maintenance for a predetermined time within the temperature between the glass transition temperature (Tg) in this invention and less than melting | fusing point (Tm) not only hold | maintains at fixed temperature but also raises / lowers temperature within temperature. Including meaning.

  In addition, when the temperature of the molten polyolefin resin is decreased and the temperature is set to a temperature within the temperature between the glass transition temperature (Tg) and the melting point (Tm), the temperature decreasing rate is the molecular chain of the polyolefin resin. As long as the orientation of the resin can be improved, it is not particularly limited, and can be appropriately set according to the type of polyolefin resin to be used. For example, when a polypropylene resin is used, the temperature lowering rate can be set in the range of 3.0 to 10.0 ° C./min.

  For example, when the molten polyolefin resin is a molten polypropylene resin and the temperature is 200 ° C., the temperature within the temperature between the glass transition temperature (Tg) and the melting point (Tm) is set to 150 ° C. It is also possible to set the temperature lowering rate to 7.7 ° C./min and reach the temperature in about 10 to 13 minutes in about 10 minutes.

  In the holding step, it is preferable that the temperature is held at a constant temperature after the temperature drop, in the above example, at 150 ° C. for a predetermined time. The time for holding the temperature at the above temperature after the temperature drop varies depending on the physical properties of the polyolefin-based resin to be used, and is not particularly limited, but is preferably 10 to 30 minutes, more preferably 15 It is preferably ~ 20 minutes.

  Further, in the holding step, the molten polyolefin resin is lowered to a temperature T1 within the temperature between the glass transition temperature (Tg) and the melting point (Tm), and then increased to the temperature T2 within the temperature. It is also preferable to warm and then hold at the temperature T2.

  In the holding step, by temporarily cooling to a temperature T1 lower than the temperature T2 within the temperature between the glass transition temperature (Tg) and lower than the melting point (Tm), the molten polyolefin resin is brought into a supercooled state, By once reducing the molecular momentum of the molecular chain constituting the polyolefin resin, and then raising the temperature from the temperature T1 to the temperature T2, the molecular motion of the molecular chain constituting the polyolefin resin is resumed, and the polyolefin resin This is considered to be because the orientation of the molecular chain can be controlled more precisely.

  The temperature T1 is preferably 10 to 50 ° C., more preferably 20 to 40 ° C. lower than the temperature T2 at which the temperature is maintained. It is preferable that the difference between the temperature T1 and the temperature T2 is 10 ° C. or more and 50 ° C. or less because the effect of the supercooled state becomes remarkable and the orientation of the polyolefin resin is improved.

  The rate at which the polyolefin system after melting is lowered to the temperature T1 and the rate at which the temperature is raised from the temperature T1 to the temperature T2 must be such a rate that adversely affects the orientation of the molecular chain of the polyolefin resin. If it is not restrict | limited especially, it is preferable that it is 50-100 degree-C / min. A temperature increase rate of 50 ° C./min or more is preferable because the effect of a supercooled state by cooling to a temperature T1 can be maintained, and a temperature of polyolefin resin is non-uniform if it is 100 ° C./min or less. This is preferable.

(Pressure process)
Next, in the manufacturing method of the polyolefin-type resin sheet of this invention, the pressurization process which pressurizes the polyolefin-type resin after the said holding process within the said temperature is provided. By pressurizing the polyolefin-based resin after melting through the holding step, the molten polyolefin-based resin can be used as the resin sheet. In the present invention, in the holding step, the temperature of the polyolefin-based resin after melting is set at a temperature within the temperature between the glass transition temperature (Tg) and the melting point (Tm) for a predetermined time. By holding, the orientation of the molecular chain of the polyolefin-based resin is firmly adjusted, so that it can be formed into a sheet by a pressure treatment under mild conditions. Examples of the pressurizing condition include 1.0 GPa or less.

(Cooling process)
Then, the polyolefin resin sheet of the present invention can be obtained by cooling and solidifying. Cooling can be carried out under conventionally known conditions using a conventionally known means, and is not particularly limited.

(Annealing process)
In the method for producing a polyolefin resin sheet of the present invention, the polyolefin resin sheet that has been subjected to the pressurizing step may be annealed under predetermined conditions. Dimensional stability can be improved by annealing the polyolefin resin.

  The annealing treatment can be performed by heating the polyolefin resin at a predetermined temperature for a predetermined time. The annealing treatment temperature is preferably a temperature not higher than the melting point of the polyolefin resin, and the annealing treatment time is preferably 1 day to 10 days. For example, when the polyolefin-based resin is isotactic polypropylene, there is a method of leaving it for about 2 to 4 days in an atmosphere at 150 ° C.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example at all.

Example 1
As the polyolefin resin, polypropylene resin (made by Nippon Polypro Co., Ltd., trade name Novatic PP “EA6A” (homopolypropylene, MFR: 1.9 g / 10 min) was used, and the polypropylene resin pellets were heated to 200 ° C. It put into the top plate and made it the molten polypropylene resin.

  Next, the molten polypropylene resin was lowered to a temperature of 155 ° C. at a temperature lowering rate of 40 ° C./min. The polypropylene resin lowered to 155 ° C. was held for 13 minutes. The molten polypropylene resin kept at a reduced temperature was subjected to pressure treatment at a temperature of 10 to 30 MPa and a temperature and time pressure shown in Table 1, and then cooled under the conditions shown in Table 1 and FIG. FIG. 1 shows an outline of temperature change (elapsed time, resin temperature of molten polypropylene) in each production process of the molten polypropylene resin.

(Melting point: measurement of [Tm])
Melting | fusing point [Tm] of the polypropylene resin sheet of Example 1 manufactured through each said process was measured. Here, the melting point [Tm] refers to the peak top temperature obtained by the following differential scanning calorimetry (DSC) measurement. The melting point [Tm] was measured with a differential scanning calorimetry (DSC) measuring machine. A differential scanning calorimeter “DSC-60” (manufactured by Shimadzu Corporation) was used as a differential scanning calorimeter (DSC) measuring instrument, and the measurement was carried out at a heating rate of 10 ° C./min.

(Measurement of crystallinity)
The crystallinity of the polypropylene resin sheet was measured by XRD (X-ray diffraction).
As a measuring machine, a fully automatic horizontal multi-purpose X-ray diffractometer “SmartLab” (Rigaku Corporation) was used. In addition, the specific calculation method of crystallinity was calculated by the following formula.
Crystallinity (%) = Crystal part peak area × 100 / (Crystal part peak area + Amorphous part area)

(Measurement of dimensional change rate)
Furthermore, the dimensional change rate of the polypropylene resin sheet was measured. The measurement of the dimensional change rate was performed by measuring the vertical dimensional change rate and the horizontal dimensional change rate of the polypropylene resin sheet according to the heating dimensional change measurement method according to JIS K7133. Here, the “longitudinal dimensional change rate” refers to the dimensional change rate in the sheet flow direction, and the “lateral dimensional change rate” refers to the dimensional change rate in the width direction with respect to the sheet flow direction. In addition, the conditions in the heating dimensional change measuring method were 150 degreeC and 30-minute heating still.

(Examples 2 to 4)
As shown in Table 1 and FIG. 1, a polypropylene resin sheet was produced in the same manner as in Example 1 except that the processing conditions of the temperature maintaining process and the pressurizing process of the molten polypropylene resin were changed. About the obtained said resin sheet, the measurement of the crystallinity degree, melting | fusing point, the vertical dimension change rate, and the horizontal dimension change rate was performed. The results are shown in Table 2.

(Comparative Examples 1 and 2)
A polypropylene resin sheet was produced in the same manner as in Example 1 except that the temperature of the molten polypropylene resin was not maintained. As shown in Table 1 and FIG. 1, in Comparative Example 1, the temperature lowering rate for lowering the 200 ° C. molten polyolefin resin was 150 ° C./min (rapid cooling), and in Comparative Example 2, the temperature lowering rate was 75 ° C. C./min (slow cooling).

  Table 2 summarizes the measurement results of the melting point, crystallinity, longitudinal dimensional change rate, and lateral dimensional change rate of the polypropylene resins of the above Examples and Comparative Examples.

  Moreover, the measurement result (X-ray diffraction: XRD) of the crystallinity degree of the polypropylene resin manufactured by the said Example and the comparative example was shown in FIGS. The measurement results in FIGS. 2 to 7 are shown in FIG. 2 (Example 1), FIG. 3 (Example 2), FIG. 4 (Example 3), FIG. 5 (Example 4), and FIG. 1) and FIG. 7 (Comparative Example 2).

  According to Table 2, the molten polypropylene resin is cooled to a temperature within the temperature between the glass transition temperature (Tg) and less than the melting point (Tm), and is maintained at the temperature for a predetermined time. It has been found that it is possible to improve the crystallinity, melting point, longitudinal dimensional change rate and lateral dimensional change rate. In particular, in Examples 2 and 3, the melting point of the raw polypropylene resin was 167 ° C., the melting point of the polypropylene resin sheet obtained through the holding step was 174 ° C., and the crystallization of the polypropylene resin It can be confirmed that the melting point is increased and the dimensional change rate is improved by improving the degree.

  Moreover, the measurement result which raises melting | fusing point of a polypropylene resin sheet can be backed up easily also from the measurement result (X-ray diffraction: XRD) of a crystallinity degree. As is apparent from FIGS. 3 and 4, the molten polypropylene resin is obtained by lowering the molten polypropylene resin to a temperature within the temperature between the glass transition temperature (Tg) and the melting point (Tm) and holding it for a predetermined time. The obtained polypropylene resin sheets of Examples 2 and 3 have four sharp intensity peaks (cps) around 12.0, 14.0, 18.0 and 22.0 (2θ [deg]), The intensity was also 250,000-300000 cps, and the crystallinity calculated from these peak intensities was 61.5 (Example 2) and 64.0 (Example 3). In FIGS. 3 and 4, it is particularly remarkable that the peak intensity can be observed sharply at 2θ = 14.0. That is, it is considered that the sharp peak of 2θ = 14.0 is attributed to the improvement in crystallinity due to the further strengthening of the molecular chain orientation of the polypropylene resin sheet.

  On the other hand, as shown in FIGS. 6 and 7, the polypropylene of the polypropylene resin sheet of the comparative example has peaks at the same positions as the above four peaks, but all of them have sharp peaks. The crystallinity calculated from the measurement results (XRD) of FIGS. 6 and 7 was about 56.0%. As is clear from the comparison between the above-mentioned Examples and Comparative Examples, the crystallinity can be improved by lowering the temperature of the molten polypropylene resin to a temperature equal to or lower than the melting point and maintaining the temperature for a predetermined time. It can be seen that the heat resistance can be improved and the dimensional change rate is also improved.

(Example 5, Comparative Example 3)
In Example 5, a polypropylene resin sheet was produced under the same conditions as in Example 2 and then annealed (heat treatment) to obtain a polypropylene resin sheet. The annealing treatment (heat treatment) was performed at 150 ° C. for 4 days. Further, as Comparative Example 3, a polypropylene resin sheet was produced under the same conditions as in Comparative Example 1, respectively, and then annealed (heat treatment) to obtain a polypropylene resin sheet. The polypropylene resin sheets obtained in Example 5 and Comparative Example 3 were measured for crystallinity (XRD), melting point, longitudinal dimension change rate and transverse dimension change rate in the same manner as Example 1. The results are shown in Table 3.

  When Example 2 and Example 5 in Table 3 are compared, by subjecting the polypropylene resin sheet to an annealing treatment, the longitudinal dimension change rate (MD) is 1.0% (Example 2) to 0.6% (Example 5). The lateral dimensional change rate (TD) is changed from 0.7% (Example 2) to 0.5% (Example 5). The value of the dimensional change rate decreases in any direction, and the dimensional stability is further improved. Turned out to be.

  That is, in the method for producing a polyolefin-based resin of the present invention, the molten polypropylene resin is lowered to a temperature within the temperature between the glass transition temperature (Tg) and the melting point (Tm) and held at the temperature for a predetermined time. Thus, the crystallinity can be improved and the heat resistance and dimensional stability of the polyolefin resin can be improved, and the obtained resin sheet can be further annealed under predetermined conditions to further improve the dimensional stability. Can be improved.

Claims (5)

A melting step of melting a polyolefin resin to form a molten polyolefin resin;
A holding step of holding the polyolefin-based resin after the melting step for a predetermined time within a temperature between the glass transition temperature (Tg) and the melting point (Tm);
And a pressurizing step of pressurizing the polyolefin resin after the holding step within the temperature.   2. The production of a polyolefin-based resin sheet according to claim 1, wherein after the temperature is lowered to a temperature T <b> 1 within the temperature, the temperature is raised to a temperature T <b> 2 within the temperature, and then held at the temperature T <b> 2. Method.   The method for producing a polyolefin resin sheet according to claim 1, further comprising a step of performing an annealing treatment after the pressurizing step.   The method for producing a polyolefin resin sheet according to any one of claims 1 to 3, wherein the polyolefin resin is a polypropylene resin.   A polyolefin resin sheet obtained by the method for producing a polyolefin resin sheet according to any one of claims 1 to 4, wherein the longitudinal dimension change rate and the transverse dimension change rate measured by a heating dimensional change measurement method according to JIS K7133. Is 1.0% or less, a polyolefin-based resin sheet.

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