JP3390230B2 - Improved thermoformable polypropylene-based sheet and process for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

This invention relates to an improved thermoformed sheet comprising at least one layer of propylene resin polymer and an effective amount of β-spherulite, a method of making such a sheet, and articles thermoformed from such a sheet. It is related to Such articles can be thermoformed with fast productivity and are microwaveable.
Can improve end use properties such as (microwaveability) and low temperature impact resistance.

[0002]

Conventional thermoformable thermoplastic resin sheets are typically manufactured from resins such as polyvinyl chloride, polystyrene based resins and the like. However, among these thermoplastics, polyvinyl chloride has disadvantages in hygiene, heat resistance, moisture resistance and other properties. Further, incineration of these materials will release chlorine-containing gas. Polystyrene-based resins are also deficient in terms of heat resistance, impact strength moisture resistance and other properties. Despite these disadvantages and inadequacies, these sheets of thermoplastic resin are widely used as thermoformed packaging materials in many fields.

The usual thermoforming method generally involves heating a thermoplastic sheet above its softening point to form the softened sheet,
Including cooling and curing. To be thermoformed by conventional thermoforming methods, polypropylene, a highly crystallized polymer, must be heated to its melting point (Tm) of 160 ° C. The flexural modulus of polypropylene can be reduced by two orders of magnitude or more at temperatures near the melting point where polypropylene sheets can undergo excessive sagging during thermoforming. Also, polypropylene does not exhibit the rubber plateau that is characteristic of glass polymers when the glass polymers are heated above their glass transition temperature (Tg). Nevertheless, polypropylene resin polymers have increasingly been used in place of polyvinyl chloride and polystyrene based resins in recent years due to their excellent strength, rigidity, heat resistance, moisture resistance and other desirable properties. ing. The market for thermoformed plastic products has grown rapidly in recent years and polypropylene-based resins have the potential to become premium materials in this market. The difficulty of thermoforming such resins limits their use in this high-growth field, as mentioned above. Many methods have been attempted to alleviate this thermoforming difficulty.

Shell Development (Shell Develop
ment Co.) developed one method. The method is SP
Utilizing the solid-state pressure molding method known as PF. The SPPF method thermoforms hot but unmelted sheet just below its crystalline melting point, but with specialized and expensive thermoforming equipment, limited draw depth, limited draw ratio, high levels of residual internals. Other constraints such as stress are introduced.

Yet another method of overcoming the difficulties of thermoforming has approached the production of polypropylene resins of specific molecular weight, which allows the extruded sheets to be processed in conventional thermoforming equipment. The melt flow rate of the polypropylene resin to reduce the degree of sagging of the heated sheets toward the crystallization temperature,
It had to be lowered to a small value, typically 0.25 dg / min. As a result, the resulting high melt viscosity causes other problems. That is, to produce the sheet at an economical extrusion production rate. To solve this problem,
Attempts have been made to improve extrudability by broadening the molecular weight distribution of propylene.

Thermoformed articles produced by the above-described method are subject to changes in dimensional integrity, depending on the products contained therein and the conditions under which the articles are microwaved.

US Pat. No. 4,680,157 shows excellent permeability and surface properties, slight stretching of the sheet and optional α-
Disclosed is a method of making a polypropylene sheet having thermoformability including a spherulite nucleating agent, a vacuum thermoformed article from a sheet heated to 153-158 ° C.

US Pat. No. 4,567,089 describes a surface layer of crystalline polypropylene and up to 5% of an inorganic or organic α-spherulite nucleating agent and a second layer of polypropylene, an ethylene polymer and an inorganic filler. Disclosed is a propylene polymer laminate sheet having surface gloss, appearance and impact resistance.

Extracting β spherulite, stretching the film,
Alternatively, a β-spheronizing agent useful for a composition forming a non-stretched film having a thickness of 0.4 mm which can be made porous by a combination of extraction and stretching, the production of a porous film and the production of a porous film. What is used in the method is US Pat.
386,129, U.S. Patent No. 4,975,469, U.S. Patent Application No. 07
/ 633,087 (filed Dec. 21, 1990, P. Jacoby et al.) And U.S. patent application 07 / 749,213 (filed Aug. 23, 1991, P. Jacoby et al.). All of these were assigned to the assignee .

The use of β-spherulite nucleating agents in a number of techniques for thermoforming sheets of polypropylene-based resins, including the formation of microporous films and the use of α-spherulite nucleating agents. Notwithstanding, there is a need for a polymer resin of propylene that can be formed into sheets under convenient conditions and under competitive productivity that can be used to thermoform articles. Such sheets are desirably thermoformable in conventional thermoforming equipment also at high production rates, and the resulting thermoformed articles exhibit end-use properties such as microwave treatability and low temperature impact resistance. Desired improvement.

The inventor has found that a polymer composition comprising a propylene resin polymer and an effective amount of a β-spherulite nucleating agent is effective for producing a thermoformed sheet, and particularly for easy and efficient production of the sheet. Expect polypropylene-based compositions with sufficient melt flow rate to be effective and effective in producing thermoformed articles from such sheets in conventional thermoforming equipment. I discovered it.

[0012]

It is an object of the present invention to provide an improved thermoformed sheet. Another object of the invention is to provide an improved thermoformed sheet comprising a propylene resin polymer and an effective amount of a β-spherulite nucleating agent. A further object of the present invention is to provide a method of thermoforming a sheet of propylene resin polymer and an effective amount of a β-spherulite nucleating agent. A further object of the present invention is to provide an article thermoformed from an improved thermoformable propylene resin polymer nucleated with a β-spherulite nucleating agent.

[0013]

Advantageously, the thermoformable sheet of the present invention contains a β-spherulite nucleating agent with a K number of about 0.3 to about 0.1.
A crystalline resin polymer of propylene with 0.95 consisting of one or more layers, the sheet comprising
-Compared to articles made from polypropylene-based resins nucleated with spherulite nucleating agents or not nucleated, the sheets are thermoformed at significantly higher production rates, the sheets having sidewall strength, warpage And the microwave treatability is improved. Further advantages are found in the embodiment of the multilayer sheet according to the invention. The multilayer sheet comprises an inner layer of a propylene resin polymer nucleated with a β-spherulite nucleating agent and an outer layer based on polypropylene such as ethylene-propylene impact copolymer with improved low temperature impact resistance.

According to the invention, a K of about 0.3 to 0.95.
Thermoformable sheets are provided that include one or more layers of beta spherulitic crystalline resin propylene included by value. According to another embodiment of the present invention, in thermoforming a sheet of propylene-containing resin polymer, (a) a polymer composition comprising a nucleating agent capable of producing an alpha spherulite and an effective amount of beta spherulite in the sheet. Melt forming, (b) quenching the melt formed sheet at a quenching temperature sufficient to produce beta spherulites included at K values of about 0.3 to 9.5; (c) the quench. Heating the sheet at a thermoforming temperature sufficient to allow thermoforming, and (d) thermoforming the heated sheet into a product using thermoforming means under thermoforming conditions. A method of thermoforming a sheet of propylene-containing resin polymer is provided.

According to yet another embodiment, a polymer composition comprising a crystalline resin polymer of propylene having alpha spherulites and the remaining nucleating agent of organic beta spherulites and a resin of propylene without organic beta spherulites residues. There is provided a thermoformed product having one or more layers of improved microwave treatability as compared to a thermoformed product containing a polymer.

Crystalline polypropylene (sometimes referred to as an isotactic polymer) can be crystallized into three crystalline forms. In melt crystallized material,
The preferred crystalline form is the alpha form or the monoclinic system. Beta or quasi-hexagonal system is present at only a few percent level if some hexagonal nuclei are not included or crystallization does not occur in the presence of shear forces or in temperature gradients. . A third crystalline improvement is the gamma or triclinic system. These are usually only observable in the stereoblock part or low molecular weight crystallized under high pressure.

The alpha form is identified herein as alpha spherulites and alpha crystals. On the other hand, the beta form is herein identified as beta spherulites, beta crystals, beta spherulites and beta crystallinity.

In the present invention, sufficient beta spherulites are compared to sheets made from alpha-nucleated or non-nucleated polypropylene in conventional thermoforming equipment when the sheets are melt-formed from the polymer. It is incorporated into a resin polymer of propylene so that it can be thermoformed at lower temperatures and faster production rates. A typical method of incorporating beta spherulites into a resin polymer is to incorporate one or more suitable beta spherulite nucleating agents into the resin polymer prior to sheet forming.

In practicing the present invention, it is preferable to use a nucleating agent to form beta spherulites in a polypropylene-based resin. HJ Leugering (Makromol. Chem. 109, p. 204 (19
67)) and A. Duswalt et al. (Amer. Chem. Soc. Div. Org. Coat., 30, N.
o.2,93 (1970)) discloses the use of certain nucleating agents which lead to the preferential formation of such beta spherulites.

As discussed by Duswalt et al., Only a few materials are known to preferentially form beta spherulite nuclei. These known beta nucleating agents include (a) gamma crystalline quinacridone colorant Permanent Red E3B having the following structural formula:

[Chemical 4] (Hereinafter, referred to as "Q-dye".) (B) Deuterium sodium salt of o-phthalate acid, (c) Aluminum salt of 6-quinizarinesulfonic acid in a smaller amount than (c), and (d) Isophthalic acid and terephthalate. Includes acid.

Similarly, German Patent 3,610,644, published March 29, 1986, discloses beta nucleating agents made from two components, A and B.
Component A is pimelic acid, azelaic acid, o-phthalic acid,
Organic dibasic acids such as terephthalic acid and isophthalic acid. Component B is an oxide, hydroxide, or acid salt of a Group II metal such as magnesium, calcium, strontium or barium. The acidic salt of component B may be derived from an organic acid or an inorganic acid, or a carbonate salt,
It may be stearate. Component B may be one of the additives already added to the propylene resin polymer. Components A and B can each be included up to 5% by weight, in particular up to 1% by weight, based on the weight of the polymer.

[0022] The nucleating agent, in order to thoroughly mix the powder and polymer resin can be dispersed in the propylene resin polymers of the appropriate methods commonly used in port Rimmer art. For example, the powder or pellet resin can be mixed with the powder, or a slurry in an inert medium can be used to impregnate or coat the powder or pellet resin. Alternatively, the powders or pellets can be mixed at elevated temperature, for example using a roll mill or by passing through the extruder multiple times. The preferred procedure for mixing is to compound the nucleating agent powder and basic resin pellets or powders and melt mix the compound in an extruder. Multiple passes through the extruder may be necessary to achieve the desired level of dispersion of nucleating agent. This type of procedure is typically used to achieve a desirable level of nucleating agent in the final product when a masterbatch of pelletized resin containing sufficient nucleating agent is blended with basic resin in a ratio of 10/1 to 200/1. To be able to get to.

The nucleating agent can be dispersed in the resin polymer of propylene according to appropriate procedures commonly used in the parimer art to thoroughly mix the powder and polymer resin. For example, the nucleating agent can be mixed with powder or pellet resin and powder, or can be made into a slurry with an inert medium to impregnate or coat the powder or pellet resin. Alternatively, the powders or pellets can be mixed at elevated temperature, for example using a roll mill or by passing through the extruder multiple times. The preferred procedure for mixing is to compound the nucleating agent powder and basic resin pellets or powder and melt mix the compound in an extruder. Multiple passes through the extruder may be necessary to achieve the desired level of nucleating agent dispersion. Generally, this type of procedure is used to achieve a desirable level of nucleating agent in the final product when a masterbatch of pelletized resin containing sufficient nucleating agent is compounded with a basic resin in a ratio of 10/1 to 200/1. To be able to get to.

For sheets formed containing beta spherulites, the content of beta spherulites in the sheet can be quantitatively defined by optical microscopy or X-ray diffraction.
In optical microscopy, thin sections made from sheets with a microtome are examined with a polarizing microscope using orthogonal poles. Beta spherulites appear as they become brighter than alpha spherulites. Beta spherulites are more birefringent. For the thermoformable sheets of the present invention, beta spherulites should have a field of view of at least 50%.

In the X-ray diffraction method, the diffraction pattern of the sheet was measured to determine the heights of the three strongest alpha phase diffraction peaks, H ₁₁₀ , H ₁₃₀ and H ₀₄₀ , and the height of the strong beta phase peak H ₃₀₀ . Compare with. The empirical parameter known as "K" is defined by the equation: K = (H ₃₀₀ ) / [(H ₃₀₀ ) + (H ₁₁₀ ) + (H ₀₄₀ ) + (H ₁₃₀ )] The value of the parameter K varies from 0 to 1.0, eg without beta crystals It is 0 for the sample and 1.0 for the sample which is all beta crystals.

For the thermoformable sheet of the present invention,
The preferred beta spherulite nucleating agent is the Q dye present at a level of about 0.1 to about 10 ppm and the value of the K parameter is
It should be in the range of about 0.3 to 0.95, preferably 0.4 to 0.85. Values of K greater than 0.95 do not provide sufficient alpha spherulite content in the sheet to support the sheet and prevent sagging of the sheet during the heating step of the thermoforming process. If the value of K is less than 0.3, the amount of beta spherulites is insufficient, and thus the sheet cannot be easily thermoformed at the beta phase melting temperature. The optimum range of values for K is about 0.4 to about 0.85. In the case of a sheet having a K value of about 0.3 to 0.95, the sheet softens at lower temperatures, allowing shorter cycle times to be used in the manufacture of thermoformed products.

Thermal analysis of thermoformable sheets can be performed by determining the beta spherulite nucleation effect by differential thermal analysis (DSC). DSC 1st and 2nd
During heating scan, parameters such as crystal point Tc and melting point Tm of alpha and beta crystal forms, heat of fusion ΔH _f, and total heat of fusion ΔH _f ^tot and beta heat of fusion of melting peak ΔH _f ^β are measured. To do. The magnitude of the ΔH _f ^β parameter indicates how much beta crystallinity was present in the sample at the beginning of the thermal scan. In general, second heating ΔH values are reported, which represent the properties of the material after melting in DSC and recrystallizing at a cooling rate of 10 ° C./min. The thermal scan of the first heating gives information about the state of the material before the heating record of the manufacturing process used to make the sample is cleared.

More specifically, in the thermoformable sheet of the present invention, various types of polyolefin resins can be used as a starting base resin, but it is particularly satisfactory when a resinous polymer of propylene is used. The result is obtained. Suitable resinous polymers of propylene include
Propylene homopolymers, propylene and ethylene or α-olefins (4 to 12 carbon atoms, particularly preferably C 4 to C 8 α-olefins such as butene-1, hexene-1, or the like of such α-olefins Random or block copolymers with mixtures). In addition, propylene homopolymer and other polyolefins (high density polyethylene, low density polyethylene,
Blends with linear low density polyethylene, polybutylene, etc.) can also be used. Preferably, the resinous polymer of propylene is polypropylene, a random or block copolymer of polypropylene, 40 mol% or less of ethylene or an α-olefin having 4 to 12 carbon atoms and a mixture thereof, a blend of polypropylene and low density polyethylene, And a blend of polypropylene and linear low density polyethylene.

The resinous polymers of propylene are also referred to herein as polypropylene-based resins, propylene-based polymers or resins, and especially polypropylene homopolymers. The resinous polymer of propylene is large enough for the easy and economical production of thermoformable sheets, and not so large as to produce sheets having undesirable physical properties (M
FR) (as measured by ASTM-1238). Typically, the MFR is about 0.5 to 20 dg
/ Min range, preferably about 1.0
To 10 dg / min. Resin MFR is 2
If it exceeds 0 dg / min, there is a drawback that the slack of the sheet increases when thermoformed due to the unreasonably low rigidity of the resin sheet. If the MFR is lower than 0.5 dg / min, difficulty will occur in shaping the sheet due to unreasonably high melt viscosity.

If desired, various other types of additives such as lubricants, antioxidants, ultraviolet absorbers, radiation-resistant agents, anti-adhesive agents, antistatic agents, etc. may be added to the resinous polymer of polypropylene. Coloring agents such as pigments and dyes, opacifying agents such as talc and TiO _2, etc. can be mixed in conventional amounts. Care must be taken not to incorporate these materials as other nucleating agents or pigments that can act as nucleating agents interfere with the proper nucleation of beta spherulites. Radical scavengers such as dihydroxy talc also have some nucleating ability and must be avoided. Inorganic materials used as whitening or opacifying agents such as TiO ₂ and CaCO ₃ are not nucleants and do not interfere with beta spherulitic nucleation. The effective amount of these additives depends on the particular application or end use required for the product thermoformed from the sheet and ranges from 0.005% to about 5% by weight based on the weight of the polymer. Can be Suitable stabilizers are the usual stabilizing compounds for polypropylene and other α-olefin polymers. Preferably, for opacifying white thermoformed articles, TiO ₂ or CaCO ₃ is added to the beta-nucleated resinous polymer of propylene at a level of about 0.5 to about 5% by weight.

Preferred antistatic agents include alkali metal alkane sulfonates, polyether modified (ethoxylated and / or propoxylated) polydiorganosiloxanes and / or C _10-20 aliphatic radicals and contain 2 C 2 _1-4 substituted with a hydroxyalkyl group,
It is a substantially linear saturated aliphatic tertiary amine. Of these, C _10-20, preferably N containing an alkyl group of C _12-18, N-bis - alkyl amine is particularly preferred - (2-hydroxyethyl).

Suitable antiblocking agents include inorganic additives such as silicon dioxide, calcium carbonate, magnesium silicate, aluminum silicate, calcium phosphate, nonionic surfactants, anionic surfactants and / or polyamides. , Polyesters, polycarbonates and other incompatible organic polymers. Examples of lubricants include higher fatty acid amides, higher fatty acid esters, waxes and metal soaps.

The melting point of the beta-type spherulites of polypropylene-based resin is generally about 144 ° C to 148 ° C,
On the other hand, the typical melting point of alpha-type spherulites is about 15
It is in the range of 9 ° C to 163 ° C. In extrusion, a sheet containing beta spherulites is heated to a temperature above the melting point of beta spherulites but below the melting point of alpha spherulites, the sheet softens sufficiently to be thermoformed and is not molten in the sheet. The alpha spherulites serve to reinforce the sheet and prevent sagging of the sheet before and during the thermoforming process. As the thermoformed product cools, the molten portion of the polypropylene-based resin recrystallizes as the higher melting alpha form. Therefore, beta crystals are essentially absent in the thermoformed product, which results in thermoformed products having physical properties at elevated temperatures comparable to non-beta spherulite nucleated polypropylene.

It has been shown that some sheets of propylene beta-nucleated resinous polymers of propylene have poor optical properties. Also, thermoformed products exhibit a "pink" color to the human eye when the Q dye level is above about 2 ppm. Since the addition of TiO ₂ does not interfere with the formation of beta spherulites, the addition of TiO ₂ to such sheets can produce excellent opaque white thermoformed products. The Q dye has been shown to be highly effective at inducing high levels of beta crystallinity at the level of 0.5 ppm, and at this concentration in the thermoformed product, human Virtually undetectable to the eye. It has also been shown that intensive blending of resin and dye in a twin screw extruder reduces the color imparted to the final resin at a given dye concentration. Other colorless latent beta nucleating agents can also be used.

Preparation of the invention, which comprises preparing a uniform composition of an effective amount of a beta spherulite nucleating agent and a resin polymer of propylene and then thermoforming the composition into a resin polymer of a propylene-containing sheet. Can be used in the method. The manufacturing method of the present invention comprises the following steps. (A) Step of melt-molding a polymer composition comprising an effective amount of a nucleating agent capable of forming beta spherulites in a sheet and a crystalline resin polymer of propylene having alpha spherulites (b) K value of about 0. Quenching the melt formed sheet at a temperature capable of forming beta spherulites at a density corresponding to 3 to 0.95; (c) heating the quenched sheet at a thermoforming temperature capable of thermoforming, d) a step of thermoforming the product from a sheet heated using thermoforming means under thermoforming conditions

The propylene resin polymer used in the method of the present invention is polypropylene; a random or block copolymer consisting of propylene and less than 40 mol% of ethylene or an alpha olefin having 4 to 12 carbon atoms or a mixture thereof; polypropylene and low density polyethylene. blend;
It is selected from a blend of polypropylene and linear low density polyethylene.

The beta spherulite nucleating agent used in the method of the present invention is
Any inorganic or organic nucleating agent can be used as long as it can form beta spherulites in the melt-formed sheet at a density corresponding to a K value of 0.3 to 0.95. Quinacridone dye Permanent Red (Perm
Anent Red) E3B has been found to be effective when used at about 0.1 to about 10 ppm by weight of the propylene resin polymer. The quinacridone dye has the following structure.

[Chemical 5]

In a broad sense, the thermoformable sheet does not have to be one layer and may be two layers, three layers or more layers. Generally, sheets having a multilayer structure can be melt formed by coextruding two or more layer components, and sheets having a single layer structure can be melt formed by extruding a single layer component. The melt molding can be performed using various known molding methods such as a calender method, an extrusion method, and a casting method. Among these, the melt extrusion slit die or T die process is particularly preferable. As an extruder used in such a melt extrusion step, an extruder having one screw or an extruder having two screws can be used. It is preferable to use an extruder that can be kneaded and extruded at a relatively low resin temperature and does not cause excessive shear stress.

In preparing a sheet that can be thermoformed by slit die, T-die or any other suitable process, the sheet extruded into the molten polymer is quenched or cooled by a suitable quenching means to solidify. . As the quenching means, one having a single quenching roll, two rolls, three rolls,
A multiple roll quench stack such as a 5 roll quench stack can be used. Such a quenching means should be capable of quenching the sheet at a rate equal to or faster than the sheet preparation rate. Also, the temperature at which the sheet is placed in the quenching means must be within a temperature range suitable to promote the formation of beta spherulites. It is preferred to use a 3-roll vertical quench stack in which the sheets are wrapped around a central roll and a bottom roll with a sheet of beta spherulites beginning at the central roll between the top roll and the central roll. The temperature of the central roll must be above 80 ° C. In order to maximize the formation of beta spherulites, 90 ° C to 130 ° C is preferable. For single layer sheets with beta spherulites, the bottom roll temperature should be about 80 ° C to 110 ° C throughout the sheet. However, if a single layer sheet with only a small amount of beta spherulites near the sheet surface and much more near the center is desired, the bottom roll temperature should be less than 80 ° C. Three
The temperature of the top roll of the roll stack is not limiting,
Be careful not to adversely affect the amount of beta type in the sheet 60
It can be set in the range of ℃ to 120 ℃. The quenching means is located relatively close to the extrusion die. The distance between the two is set depending on the roll temperature, the sheet extrusion speed, the sheet thickness and the roll speed, but generally about 0.25 to 5 cm.
To The speed of the quenching step can be faster than the extruded sheet preparation rate to draw down the extruded sheet. Since the sheet prepared by this process is drawn in only one direction, the transverse and longitudinal strength properties are not uniform.

In preparing a multi-layer sheet having a beta spherulite nucleation resin polymer layer of propylene by coextrusion, one extruder is used to extrude the beta spherulite nucleation resin sheet and at least one of the nucleation resins is used. Another extruder may be used to contact the non-nucleated polymer resin layer on one side between nip rolls and to coextrude them. If you want to provide the non-nucleating resin layer on both sides of the beta nucleating resin,
A method of pouring the non-nucleated polymer melt between the two slit dies by bringing one surface of the beta nucleated polymer resin layer into contact with the second layer of the extruded sheet between the nip rolls. Alternatively, one or more extruders may be used to feed the molten polymer into a coextrusion die that can simultaneously extrude two or more polymer layers from a given slit die. To prevent the polymer from freeze-off at the die lip, the temperature of the die used is adjusted with a die lip heater to be at or slightly above the resin melting temperature. In order to prepare a sheet with a smooth surface, the surface of the die should be free of damage and scratches.

Single-layer or multilayer sheets produced by extrusion, lamination, or other methods are thick enough to be thermoformed without excessive slack in the thermoforming process, and in the receiving area. It can have a thickness that is not too thick to be thermoformed. Typically, the thermoformable sheets of the present invention have a thickness of 0.25 mm or greater and range from about 10 to about 200 mils. The multilayer sheet has a beta-nucleated polymer resin of about 10 to about the sheet thickness.
It can have a structure such that it comprises about 99.9% and the non-nucleated polymeric resin comprises about 90 to about 0.1% of the sheet thickness. Preferably, in the three-layer sheet, the inner sheet is a beta-nucleated polymer resin and has a sheet thickness of about 50-.
It comprises about 99.5% and the outer two layers are a non-nucleated polymer, accounting for about 0.5 to about 50% of the sheet thickness. The outer layers may be of substantially the same thickness or different thicknesses. Preferably, each of the outer layers can have a thickness of about 0.01 to about 0.1 mm and the intermediate layer can have a thickness of about 0.23 to about 4.5 mm. Such multilayer sheets can combine different resins using two or more extruders. Resin polymers of propylene for multilayer sheets include, for example, polypropylene homopolymers, random or block polymerized ethylene-propylene copolymers, polypropylene with different melt flow rates, adhesive polyolefins modified with polypropylene and unsaturated carboxylic acids or their derivatives,
It may be polypropylene and polyethylene or ethylene-vinyl acetate copolymer, polypropylene and ethylene-vinyl alcohol copolymer, beta spherulite nucleated polypropylene and polypropylene and the like. In thermoformable sheets or thermoformed products having three or more layers, the inner layer can be used as a tie layer to join the outer polymer layers, or the inner layer can be
It can be a gas / chemical barrier layer to provide gas or chemical resistance. Alternatively, such a multilayer sheet can be formed by other known methods such as laminating a winding sheet with heat and / or an adhesive tie layer, or laminating a winding material into a sheet shape at the time of extrusion.

For multilayer thermoformable sheets that have been thermoformed into products that provide protection by gas and chemical barriers, the barrier layer is typically poly (ethylene vinyl alcohol) (EVOH), poly (vinylidene chloride), or the like. The polymer matrix such as various nitrile polymers described above is used as a polar polymer, and the polymer such as polyolefin is used as a moisture-proof nonpolar polymer.

As a gas / chemical barrier polymer, EVO
As the H polymer, those having an ethylene content in the range of 29 to 44 mol% can be used. The typical copolymer used is EVA sold by Kuraray Co. Ltd.
L grade, Soa marketed by Nippon Gohsei
marketed by rnol grade and DuPont Co.
It is Selar OH grade. Other blocking polymers are Bare
high nitrile polymers such as x210 and Barex 218 (high acrylonitrile-methyl acrylate copolymer grafted onto preformed poly (butadiene-acrylonitrile) elastomer); high acrylonitrile-styrene copolymers and terpolymers;
High acrylonitrile-indene copolymers and terpolymers; and high methacrylonitrile content homopolymers, copolymers and terpolymers. Other blocking polymers which can be used are all customary homopolymers, copolymers or terpolymers based on vinylidene chloride.

Other typical blocking polymers include poly (vinyl chloride); methyl methacrylate-styrene copolymer graft-polymerized on diene elastomer; Tr
Amorphous polyamides such as ogamid T; crystalline polyamides such as nylon-6 and nylon-66; polyesters such as polyethylene terephthalate and poly (ethylene 2,6-naphthalene dicarboxylate); polyurethanes; polycarbonates; polyphenylene oxides; polyphenylene oxides. / Polystyrene blend; polystyrene; containing polyetherimide and polyalkylmethacrylate.

The polymer of the inner layer is selected on the basis of other functions to be imparted to the system, such as high temperature resistance. In this case, usable polymers are polycarbonate, polyethylene terephthalate, poly (ethylene 2,
6-naphthalene dicarboxylate), polyphenylene oxide, polysulfone, polyetherimide, thermoplastic polyimide and polybenzimidazole. The additional polymer layer for the inner layer should not adversely affect the improved thermoformability of beta spherulites containing a resin polymer of propylene. Preferably, the intermediate layer further comprises a crystalline resin polymer of propylene and a balance of organic beta spherulite nucleating agent or ethylene vinyl alcohol copolymer.

Combinations of specific polymer compositions may be used in one or both of the outer two layers of the sheet having three or more layers. In a thermoformable sheet consisting of a beta spherulitic intermediate layer containing a propylene resin polymer and an outer layer of a thermoplastic resin, the propylene resin polymer is polypropylene, propylene and up to 40 mol% ethylene or 4-12% ethylene. The thermoplastic resin is selected from the group consisting of random or block copolymers with α-olefins having carbon atoms, blends of polypropylene with low density polyethylene, and blends of polypropylene with linear low density polyethylene, the thermoplastic resin being polypropylene, propylene and 40 Random or block copolymers with up to mol% ethylene or α-olefins with 4-12 carbon atoms, blends of polypropylene with low density polyethylene and polypropylene with linear low density polyethylene, about 1-20 w.
It is selected from the group consisting of block ethylene-propylene copolymers having an ethylene content of t%, blends of ethylene-propylene rubber polymers with high density polyethylene, and blends of ethylene-propylene rubber polymers with low density polyethylene.

For example, a modified polypropylene copolymer having high impact resistance is used for the outer layer and a beta-nucleated material is used for the intermediate layer to obtain a thermoformable sheet having a high thermoforming rate and improved low temperature impact resistance. Thermoformed articles of manufacture can be produced.

To optimally shape the beta spherulites in the melt-formed sheet, the quenching temperature in step (b) is about 90.
C to about 130 ° C. The thermoforming temperature of step (c) should be sufficient to melt the beta spherulites, but not the alpha spherulites. Typically, the beta-spherulite form of polypropylene has a melting point of about 144 ° C.
~ 148 ° C and the melting point of the alpha spherulitic form of polypropylene is about 159 ° C to 163 ° C. By heating the quenched sheet to about 144 ° C to 148 ° C, the beta spherulites soften and the sheet can be thermoformed. The alpha spherulites remain in the solid state, imparting cohesiveness to the sheet and preventing excessive sagging of the sheet during thermoforming.

The thermoforming temperature in step (c) is from 144 ° C. to 14 ° C.
In certain embodiments of the method of the present invention below the melting point of the beta spherulites at 8 ° C, the thermoformed article of step (d) tends to "microbode". Microvoiding means the formation of minute voids in the sidewalls of thermoformed articles. This microvoiding will produce an opaque white thermoformed article in the absence of filler. The side walls of these containers are
It has about 2 to about 20% less density than the sheet of raw material. Microvoiding yields low density sidewalls,
Still, the manufactured product is binding and moisture proof.

The thermoformable sheets of the present invention can be thermoformed by conventional thermoforming equipment and methods including in-line with sheet cast extruders or off-line with a feed-fed thermoformer. it can. The conventional thermoforming method is
Vacuum forming, pressure forming, plug assist pressure forming and Th
e Encyclopedia of Polymer Science & Engineering
(Polymer Science and Engineering Dictionary), John Willy & Sons, Vol.
16, p. 807-832, 1989, including matched mold thermoforming. Such thermoforming refers to (a) heating a thermoplastic sheet until it softens, (b) molding the softened sheet in a mold under the influence of gravity, pressure and / or vacuum, and (c) molding It is a method for producing a product from a thermoplastic sheet, which generally includes a series of steps in which the sheet is cooled, solidified, cut out from the sheet, stacked and packaged. Basic thermoforming changes include size cutting, roll feeding, or in-line extrusion sheeting; sheet heating materials such as metal sheath radiant heaters, quartz radiant heater panels, ceramic heaters, convection ovens, contact heating; molds; Vacuum or pneumatic forming; in-situ or in-situ trimming; and packaging and the like. Lower pressures are generally used in the thermoformed sheet method of the present invention as compared to thermoformed non-beta nucleated polypropylene sheets. The thermoforming process of the present invention can also be performed in-line during the production of the thermoformable sheet, or off-line from the roll of sheet material. Preferred thermoforming methods include vacuum forming and plug assist pressure forming.

Various combinations of polymers and layers can be used with the β-nucleated crystalline resinous polymer of propylene to make the thermoformable sheets and thermoformed articles of the present invention. For example, in a multilayer with β-nucleated material as an intermediate layer, the intermediate layer further comprises a crystalline resinous polymer of propylene and a residue of an organic β-spherulite nucleating agent such as a Q-dye. It consists of ethylene vinyl alcohol copolymer or regrind material.

Such sheets can be thermoformed at lower temperatures and faster cycle times than required for resinous polymers of propylene without β-spherulite nucleating agent. Under these conditions of lower temperature and faster cycle time,
Sheet slack was less of a problem, less heat was required to peel it from the sheet, the thermoformed product finished faster, and wider supportless sheets could be used in thermoforming operations.

Thermoformed articles of the invention are typically used in automotive applications such as bumpers, truck bed liners, fender wells, door panel inserts, glove box doors, etc .; travel bags, trays, storage trailers, ice cooler liners. , Ice cube tray,
Consumer applications such as toys and signs; household appliances such as refrigerator door liners and freezer panels; household items such as cups, shower stalls, sinks and tubs; boat hulls, golf cart canopies, bicycle wheel covers, ski mobile hoods, and Recreation products such as shrouds; and containers and lids for food and beverages in general;
And yogurt cups, margarine tubes, cottage cheese containers, shipping containers, frozen food trays, lids, meat trays, fast food disposable products and other packaging applications. We can also manufacture products molded from thicker sheets with deeper drawing. Preferred thermoformed products are food containers and products with low temperature impact resistance.

X-ray diffraction data was measured on specimens taken from various parts of thermoformed products made from different resins. No β-diffraction peak was evidenced for any of the thermoformed samples. It is known that when the β phase melts but the remaining α phase does not melt, the melted polymer recrystallizes as the α phase only. This is because the unmelted α crystal directs the recrystallization process. Thus, the thermoformed product, on the contrary, does not have β-crystallinity, which has the same temperature properties as non-β-nucleated material. Although the thermoformed product does not contain non-β spherulites, the product can be analyzed for the nucleating agent because of the residual β spherulite nucleating agent and residues of the nucleating agent. Alternatively, the thermoformed article made from β-nucleated material can be reground under the appropriate conditions described above to form a sheet with β spherulites. The material thus reground can be used alone or in combination with virgin β-nucleated material, any such material being sufficiently compatible that the reground material is It must be free of materials that interfere with the nucleation of spherulites.

[0055]

EXAMPLES It will be appreciated that the following examples serve to illustrate the invention in greater detail and are not intended to limit the scope of the invention.

Reference Examples 1-4 and Control Reference Example A

Cast sheets were made from a nucleated polypropylene resin containing different amounts of β-spherulite nucleating agent. The β-nucleating agent is
It was E3B, a red quinacridine dye commercially available from Hoechst Celanese. A masterbatch of Q-dye at a level of 200 ppm was prepared with Q-dye and polypropylene powder (Am
ASTM D1238 obtained from oco Chemical Company
Polypropylene with 3.1dg / min of MFR, as measured by
Pyrene Grade 9103 powder ) as a powder blend. This masterbatch was prepared with a final concentration of 1. Q dye in polypropylene resin having an MFR of 3.1 dg / min.
It was made to be 0, 1.5, and 2.0 ppm. 0.18 based on these resin blends based on resin weight
% Of sterically hindered phenol (trademark "Irga from Ciba"
Pentaerythritol sold as "nox 1010"
Tetrakis [3- (3,5-di-tert-butyl-4-hydroxy]
Cyphenyl)] Propionate) , Phosphonite (Sandoz
Sold by the company under the trademark "Sandostab P-EPQ"
And a stabilizer mixture of calcium stearate
(Sterically hindered phenol: Phosphonite: Stearic acid
Stabilized with Lucium = 2: 2: 1) and pelletized on a 63.5 mm Prodex extruder. The above resin and a control polypropylene resin with MFR 2.5 dg / min and no nucleating agent were processed into cast sheets on a 38 mm Davis Standard extruder cast sheet line under the following conditions:

[0058]           Polymer melting temperature, ° C 227           Extruder screw rotation speed, rpm 25           Extruder die gap, mm 0.508           Sheet production rate, m / s 0.017           Sheet thickness, mm 0.406           Chill roll temperature, ℃ 108           Air knife pressure, psi 40

The product of Reference Example 1 has a Q dye concentration of 1.0 pp.
m polypropylene compositions and the products of Reference Examples 2 and 3 were made from polypropylene compositions having Q dye concentrations of 1.0 ppm and 2.0 ppm, respectively.
The reference product, Reference Example A, contained no Q dye. Reference Example 4 had the same polypropylene and Q dye concentration as Reference Example 3, but with an extruder screw rpm of 25 to 40.
Accelerated to rpm, the sheet production speed was also accelerated from 0.017 to 0.028 m / s. Both the polypropylene-based composition and the sheet were characterized by DSC. The β crystal content of the sheet of each reference example was determined by the K value measurement of X-ray diffraction. These sheets were probably thick enough to be anisotropic, so X-ray diffraction was performed on both the air knife side and the chill roll side of each sheet. The polymer composition properties are summarized in Table I. Table I contains the Q dye concentration, the composition MFR, the α spherulite melting temperature T _m α, the β spherulite melting temperature T _m β, and the crystallization temperature T _c . Sheet properties are summarized in Table II. Table II contains the K values and crystallinity for both the air knife side and the chill roll side of each sheet.

[0060]

[Table 1]

[Table 2]

Reference Example 5-8 Polypropylene-based composition containing four different levels of Q-dye, NA-10 nucleating agent (sodium bis (4-t-butylphenyl) phosphate) and nucleating agent The control without is a nucleating agent-containing polypropylene resin (based on the weight of the resin) stabilized with 0.18 wt% (based on the weight of resin) of a commercial antioxidant and a treatment stabilizer as described in Reference Examples 1-4. Base polypropylene resin is based on Amoco Chemical Compa
Polypropylene Grade 9103 powder obtained from NY). The composition was melt mixed and 63.5 m
m prodex extruder pelletized after mixing and pelletizing, TiO ₂ 5 wt% pellet concentrate, Ti
A propylene resin with 50 wt% O ₂ was dry blended with each of the resin compositions. The resin blend was then extruded on a 63.5 mm DNR MPMIV sheet extrusion line into 40 mil thick sheets. The temperature of the 3-roll cooling stack in the extrusion line is 1 for the upper roll.
10 ° C and 104 ° C on middle and lower rolls.

The composition of Reference Example 5 had a Q-dye concentration of 0.5 ppm. The compositions of Reference Examples 6, 7 and 8 had Q-dye concentrations of 1.0, 2.0 and 4.0 ppm, respectively. Control C had no added Q-dye. Control D is NA-1 present at a concentration of 850 ppm
Had 0 nucleating agent. The polypropylene base resin and extruded sheet are characterized by DSC and X-ray diffraction. The properties of the polymer composition are Q-dye composition, α spherulite phase melting temperature T _m α, β spherulite phase melting temperature T _m β, crystallization temperature T _c , total melting heat ΔH _f ^tot and β. The heats of fusion ΔH _f β of the phase melting peaks are summarized in Table III. The properties of the extruded sheet, including the thermal properties of the DSC first and second thermal scans, are summarized in Table IV.

[0063]

[Table 3]

[Table 4]

From the data in Tables III and IV, the most interesting parameters from the thermal analysis relating to the nucleation effect are the crystallization temperature T _c and the heat of fusion ΔH ^β _f of its beta-melting peak. As the density of nucleation centers increased, T _c increased. The magnitude of the ΔH ^β _f parameter is a measure of how much beta crystal is present in the sample at the beginning of the thermal scan. The second heat ΔH value is generally reported and there is a representative of the material properties after being melted and recrystallized in DSC at a cooling rate of 10 ° C / min. The first thermal scan provides information about the state of the material before the thermal history of the processing steps used to make the sample disappeared.

From the second thermal scan data in Tables III and IV, the polymer composition shows a peak in beta crystallinity at a concentration of 1.0 ppm nucleating agent, while the extruded sheet had a pH of 0. It can be seen that it showed this peak with beta nucleating agent content at a concentration of 5 ppm. It is believed that the tendency for the presence of maximum concentration of beta crystallinity with increasing nucleating agent concentration is due to the Q-dye nucleating the alpha and beta crystal forms of polypropylene. This alpha form begins to crystallize before the beta form,
And if sufficient high concentrations of nucleating agent particles are not present, morphology can be favored. The concentration of beta crystallization that develops depends not only on the nucleating agent concentration, but also on the degree of dispersion of the nucleating agent particles and the thermal conditions used to crystallize the material. The sample made from the extruded sheet differs from the base resin sample in two ways. First, the sheet sample goes through an additional mixing method. This may have played a role in changing the dispersion of nuclear particles. Second, the sheet sample contained 2.5% TiO ₂ , and this may also have affected crystallization behavior.

The significant effect of thermal history on the crystallization morphology of the sample is apparent by comparing the first and second thermal scans of the extruded sheet. The thermal scans of Reference Examples 5, 6 and 7 with β-nucleating agent concentrations of 0.5, 1.0 and 2.0 ppm, respectively, all have significant β-melting peaks associated with the other sheet samples. The results suggest that the β-content maximum is broad in the sheet compared to the resin and extends from 0.5-2.0 ppm Q-dye. Low levels of β crystallinity are seen in Control B, which contains no nucleating agent, and no evidence of β phase formation is usually apparent in the α-nucleating agent-containing material (Control C). Is notable.

Articles were thermoformed from the extruded sheets of Reference Examples 5, 6 and 7 and Controls B and C using a Plastlform Labform Model 1620 PVICP thermoformer with a 12 ounce "Cottage Cage" cup mold. . The heater of the thermoformer has three different sets, 315 ° C (600
° F), 371 ° C (700 ° F) and 427 ° C (800
It was set at ° F). The thermoforming evaluation was carried out at three different heater settings with a standard setting of 427 ° C. for evaluating the thermoforming properties of polypropylene. The lower the heating temperature, the longer the circle time required to make an acceptable looking cup. At each temperature, the heating time was varied to determine the upper, upper and lower operating limits of the heating time. The lower limit represents the minimum time required to make an acceptable part, which limits the part where wall thickness uniformity and mold profile replication are acceptable.
Above the upper limit of time, the sheet was too soft and a temperature drop and sticking of the sheet to the plug was observed.

The X-ray data obtained on the extruded sheet samples are summarized in Table V. X-ray measurements are made on both sides of the sheet. Because the heat history of the two sides is somewhat different. From this data, the highest level of β crystallinity, as measured by the K-value, is Q-
It was obtained with sheets containing 0.5, 1.0 and 2.0 ppm of dye, which is found to be in agreement with the thermal data discussed above. Reference Example 8 containing 4.0 ppm of Q-dye showed a large discrepancy in K-values from one side of the sheet to the other, suggesting that this material was particularly sensitive to changes in heat history.

The resins exhibiting the highest mold filling properties were Reference Examples 5, 6 and 7. These are the highest K
-Is a reference example showing the -value and the maximum amount of β-crystallinity in the first thermal DSC scan. The sample with the lowest degree of mold filling was the normal α-forming nucleating agent-containing resin (Control C) without β crystallinity as revealed by X-ray and thermal analysis.
Met. Control B, which had a low level of β crystallinity, had an intermediate mold fill. The thermoformability of these sheets, apparently at low heating times, accurately reflects the β crystallinity present in the sheet.

The optimum thermoforming window of these resins at a heating setting of 427 ° C.
w) is listed in Table VI and the wide processing window indicates that the extruded sheet resin is present in Reference Examples 5, 6 and 7 of these resins which contained high levels of β crystallinity. Similar data obtained at 316 ° C and 371 ° C heater settings are also summarized in Table VI.

[0071]

[Table 5]

[Table 6]

Reference Examples 9-11 Each of the polypropylene-based compositions was based on the weight of the resin, a sterically hindered phenol (trademark "Irga" from Ciba).
Pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl)] propionate), sold as "nox 1010", phosphonite (Sandoz
Marketed under the trademark "Sandostab P-EPQ") and a stabilizer package of calcium stearate (sterically hindered phenol: phosphonite: calcium stearate = 2: 2: 1) stabilized with 0.18% by weight nucleating agent. Prepared from additive polypropylene resin (base polypropylene was polypropylene Grade 9103 powder obtained from Amoco Chemical Company). These compositions contain two different concentrations of Q-dye or one concentration of alpha spherulite nucleating agent, NA-10 (bis (4-tert-butylphenyl) phosphate) and are described in Reference Example 1. It was prepared as described above. These compositions were melt compounded and pelletized on a Japan Steel Works CIM extruder. After compounding and pelletizing, by adding TiO ₂ in the state of the TiO ₂ 50 wt% concentration (P-8555 commercially available from A.Schulman, Inc.) in the composition and the TiO ₂ concentration of 1% by weight. These compositions were extruded into sheets of varying thickness. The composition of Reference Example 9 had a Q dye concentration of 0.75 ppm and contained no TiO ₂ . Q in Reference Example 10
The dye had a concentration of 0.75 ppm and contained 1% by weight of TiO ₂ . The composition of Reference Example 11 had a Q dye concentration of 1.5 ppm,
Comparative Example D contained a non-β spherulite nucleating agent at a concentration of 850 ppm.
The 70 mil sheet was a 89 mm Welex extruder with three stacked chill rolls, the upper roll temperature range was 71.7 to 73.3 ° C, and the middle roll temperature range was 101.1 or 102.8. The temperature range of the lower roll was 79.4 to 80.6 ° C. 17
11 mil, 25 mil and 48 mil thick sheets
4 mm Welex Extruder with 3 stacked cooling rolls, upper roll temperature 60 ° C, middle roll temperature range 97.8-102.8 ° C and lower roll temperature range 81.1-85. It was 6 ° C.

Off-line thermoforming of 25 mil sheets was done on a rectangular tray mold Armac thermoformer.
Off-line thermoforming of 48 mil sheets is Gabler
A 743 thermoformer was used with a 16 ounce deli cup mold and the lid of the 16 ounce cup was manufactured on a Gabler lid thermoformer using a 17 mil sheet. Off-line extrusion was performed using a Welex 114 mm extruder to produce sheets of 17, 25 and 48 mil thickness. The sheets were thermoformed into 16 ounce container lids, rectangular trays and 16 ounce deli cups, respectively. All of these sheets had 2 wt% P-8555TiO _{2 to} give a final TiO ₂ concentration of 1%.
Was prepared from a polymer composition containing

The main differences in the appearance of the sheets included the light pink color of the sheets of Reference Examples 9 and 10, and the slightly lower gloss on the back surfaces of these two β-nucleating agent-added sheets. The back surface of the sheet is the surface that comes into contact with the middle chrome roll, and when a section cut from this sheet is observed under a microscope, the concentration of β spherulites on this surface of the sheet was high. Presumably the β spherulites caused some defects on this side of the sheet, which reduced gloss.

Samples from these sheets were then X-ray analyzed for crystal type distribution. The K-values obtained from both the top and bottom surfaces from each sheet are shown in Table VII.
The control D sheet contained no β crystals. For the sheets prepared from the β-nucleating agent-added resin, Reference Examples 9, 10 and 11, the β crystal content on the back surface of the sheet was generally high. This effect is probably due to the increased temperature of the backing of the sheet when in contact with the middle roll. 25
For the mil-thick sheet, one sheet without TiO ₂ was also produced, whose K-value was almost the same as the sheet of Reference Example 9 made from the same resin after adding TiO ₂ , _{Although 2} had little or no effect on crystal nucleation, it was suggested that TiO ₂ still contributes to the formation of a more uniformly white and opaque sheet. Two
For a 5 mil thick sheet, the amount of Q dye is 0.7
Increasing from 5 to 1.5 ppm produced a very small effect on the K-value. 17 mil thick sheet has the lowest K
-Value, which may be due to the fact that this sheet had a short contact time with the middle chrome roll due to the high line speed. The 48 mil thick sheet had a K-value of 0.79 which was also high on both sides.

A tray using the 25 mil thick sheet of Reference Example 11 was prepared using standard conditions of 14.5 cycles per minute (cpm). Under these conditions, the tray appeared to be fully satisfactory. Increase production speed 15
After cpm, some side wall contour was lost. Reference example 9
The tray made from the sheet of Example 1 appeared to have a better material distribution than the tray of Reference Example 11 and no loss of sidewall contour occurred at speeds above 16 cpm. The β-nucleated sheet provided a 10-15% improved article manufacturing rate on the thermoformer and provided a tray with superior overall material distribution and sidewall strength compared to pure polypropylene resin. A 16 ounce cup lid was manufactured from a 17 mil sheet of the resin of Reference Example 11 on a Gabler lid maker. The machine operated at a maximum speed of 15 cpm when using a non-β nucleating agent-loaded propylene resin. Warping of the lid was observed at higher speeds. When the sheet of Reference Example 11 was used, the speed was increased to 20 cpm without any problem of warpage, and the production efficiency was improved by 33%. A 16 ounce container was thermoformed from a 48 mil thick sheet using a Gabler 743 thermoformer. Thermoforming was started with pure polypropylene at a speed of 14.9 cpm. When the process was switched to the sheet of Reference Example 9, the appearance of the container was dramatically improved. The production rate was increased to 18 cpm with excellent material distribution and no warpage as observed. The cups made from this sheet had a lustrous appearance and had a matte type finish on the inside.
The outer surface of the cup in this case corresponded to the upper surface of the extruded sheet. The sheet roll was turned over so that the top of the sheet was on the inside of the cup, with a matte finish on the outside of the container.

[0077]

[Table 7]

Various analyzes were performed on these 16 ounce cups and the results are shown in Table VIII. For the sidewall profile of cups made from beta nucleated resin at 16, 17 and 18 cpm, compared to pure polypropylene,
The wall thickness was improved. Increasing the cycle rate from 14.9 to 18 cpm did not cause any significant adverse effect on the beta nucleated resin on any of the important properties of the container.

[0079]

[Table 8]

The tests were carried out on these containers using both water and spaghetti sauce in a microwave oven (microwave oven) set to "high" for 5 minutes. 0.
The container made from the composition containing 75 ppm of Q dye (Reference Example 9) showed no substantial bending or distortion after the microwave resistance test. In contrast, Control D
The containers made from the sheets of the sheet produced considerable strain during testing. This difference in behavior is believed to be due to the low residual molding stress in the containers thermoformed from β-nucleated sheets.
This is because the β phase melts before thermoforming.

Example 12 A homopolymer composition of polypropylene without β-spherulite nucleation, two outer or skin layers, and a polypropylene homopolymer composition with β-spherulite nucleation as the inner or core layer. A multi-layer thermoformable sheet having These two compositions consist of hindered phenols (from Ciba
Pentae sold under the trademark "Irganox 1010"
Lithritol tetrakis [3- (3,5-di-tertiary-butyl
-4-Hydroxyphenyl)] propionate) , phosphonite (trademark "Sandostab P-EPQ" from Sandoz )
Marketed ) and a stabilizer package consisting of calcium stearate (hindered phenol: phosphonai)
To: calcium stearate = 2: 2: 1) was stabilized with 0.18% by weight, based on the weight of the polymer. The composition of the skin layer was 12-5013 grade polypropylene, commercially available from Amoco Chemical Company, with an MFR of 3.8 dg / min. The polypropylene resin of the composition of the core layer has an M of 3.0 dg / min.
Homopolymer of polypropylene with FR and 0.75 ppm Q dye (base polymer is Amoco Chem
Polypropylene Grade 9103 powder obtained from ical Company
It was the end) . These compositions are manufactured by Japan Steel
A Works (Japan Steel Works) CIM extruder was used to melt mix and pelletize under conventional polypropylene operating conditions. After mixing and pelletizing, 5 wt% P-8555 (50 wt% TiO ₂ concentrate) was added to the composition, based on the weight of the polymer. 89 mm core layer of multilayer sheet
Extruded using a Welex extruder, and the skin layer was extruded using a 63.5 mm extruder. The total sheet thickness was 48 mils, including the core layer and 2 mil thick skin layers on both sides thereof. At the measured temperature of the roll surface, the 3-layer sheet was extruded into a 3-roll cooling stack consisting of a 74 ° C. top roll, a 98 ° C. middle roll, and a 82 ° C. bottom roll, respectively. Dynatup impact strength was measured on the extruded sheet at -20 ° C with a measured maximum load of 41.3 pounds and a measured maximum energy of 0.21 foot-pounds.

Example 13 A three-layer thermoformable sheet was prepared using the same processing conditions and equipment as described in Example 12. The composition of the core layer has an MFR of 3.0 dg / min and 0.75 ppm
Polypropylene homopolymer with Q dye (base
The polymer is a poly obtained from Amoco Chemical Company.
Propylene Grade 9103 powder) 50% by weight and 3.0
dg / min polypropylene resin having an MFR (Besupo
The limmer is a polyp obtained from Amoco Chemical Company.
Ropylene Grade 9103 powder) and 0.75pp as residual amount
Normal 50/5 with m dye and 1.5 ppm Q dye nucleating agent
0% regrind mixture 50% by weight. The composition of the epidermis layer is PD7292N grade 3.5 dg from Exxon.
It was a high impact ethylene-propylene copolymer with an MFR of 1 / min. Dynatup impact strength was measured on the extruded sheet at -20 ° C with a measured maximum load of 206.8 pounds and a measured maximum energy of 2.08 foot pounds. Example 1
Sheets 2 and 13 were thermoformed by both in-line and off-line thermoforming using a 16 ounce deli cup mold. Production rates of 18 cpm or higher were achieved during offline thermoforming of both the sheets of Examples 12 and 13. The containers made from the sheets of Examples 12 and 13 had excellent appearance, good contours and good sidewall distribution. A production rate of 18 cpm means a 20.8% increase in production with a 16 ounce delicate cup mold compared to the typical production rate of 14.9 cpm for a non-nucleated polypropylene composition. Various analyzes were performed on these 16 ounce cups. A summary of the results is shown in Table IX.

Microwave oven for the container of Example 12
A bun (microwave oven) test was performed. 18.1-18.3
16 with the water of Example 12 produced at a rate of cpm
Micro with an ounce deli container set high for 5 minutes
I put it in a wave oven (microwave oven) . All 15 containers were held without any visible strain or shrinkage. Fifteen 16 ounce deli containers containing the water of Example 12 made at a rate of 18.7 cpm were
Microwave oven (electronic tray) set to "high" for 5 minutes
) . Bubbles were bubbled out at the bottom of some of these vessels after microwave testing. 1
The containers manufactured at the high thermoforming rate of 8.7 cpm also seemed to be usable once. The higher thermoforming rates achieved with coextruded sheets having a core layer of beta nucleated polypropylene have been shown to improve the thermoformability of such coextruded sheets. The 16 ounce bowls made from both Examples 12 and 13 had no pink coloration visible to the human eye, with a slight hint of pink coloration when stacking multiple bowls.

[0084]

[Table 9]

A microwave oven (microwave oven) and freeze drop test were performed on the container of Example 13. 15 ~
Twenty thermoformed containers at a production rate of 18 cpm were filled with 340 g of product (salad), frozen at -18 ° C, removed from the freezer and dropped from a height of 3 feet onto a concrete floor. The containers held well during the test, some trays stopped at their corners, and some bounced and flipped over. Then, the microphone was set these container to "high" for 8 minutes
It was subjected to a microwave oven (microwave) test. All my
The microwave oven (microwave) container holds well,
Maintained a good appearance.

Example 14 and Controls E-K The compositions of Example 14 and Controls E-K were tested for the β spherulite nucleation efficiency of the Q dye, including other β nucleating agents, and nucleating agents. Compared to no control. All nucleated agents were fine powders. 0.18% by weight, based on the weight of polymer, of nucleating agent and stabilizer package (hindered phenol (Ciba
Marketed under the trademark "Irganox 1010"): Phosphonay
(Sold by Sandoz under the trademark "Sandostab P-EPQ"
(Sold): calcium stearate = 2: 2: 1) was added to various resin polymers of polypropylene and mixed using a 19 mm Brabender extruder. With this brave bender extruder, 1
The sheet was extruded using a 5.2 cm wide slit die and a three roll cooling stack with a center cast roll temperature of 90 ° C.

Control E was prepared with a nucleating agent consisting of a 50/50 weight ratio mixture of terephthalic acid / calcium oxide of 1,1.
2.0 dg content at 0 or 100 ppm level
Polypropylene homopolymer with nominal MFR / min ( 6200P series resin obtained from Amoco Chemical Company )
Manufactured from.

Control F is a nucleating agent consisting of a 50/50 weight ratio mixture of azelaic acid / barium oxide, 1, 10,
Or containing at a level of 100 ppm, 2.0 dg /
Polypropylene homopolymer with nominal MFR of 6 minutes ( 6200P series resin obtained from Amoco Chemical Company )
Manufactured from.

Control G contains no nucleating agent, 2.0
Polypropylene homopolymer with nominal MFR of dg / min ( 6200P series tree obtained from Amoco Chemical Company
Fat ).

Control Example I has a nominal MFR of 2.0 dg / min.
Polypropylene homopolymer with 27.4% (Amoc
o 6200P-based resin obtained from Chemical Company) with an ethylene content of 40% by weight and a nominal M of 1.0 dg / min.
50% by weight of ethylene / propylene block copolymer with FR, 5% by weight of low molecular weight polypropylene having a melt viscosity of 112 poise measured at 190 ° C. and a shear rate of 136 sec ⁻¹ , and CaCO ₃ (17.6).
(Wt%) made from a resin polymer of propylene.

Control H is a polypropylene homopolymer having a nominal MFR of 2.0 dg / min ( Amoco Ch) containing a nucleating agent consisting of a 50/50 weight ratio mixture of 1000 ppm azelaic acid and 1000 ppm CaCO _3.
6200P resin obtained from emical Company ).

Control J was prepared from a blend of the propylene resin polymer of Control I and azelaic acid 100 ppm.

Control K was prepared from a blend of the resin polymer of propylene of Control I and 1000 ppm barium oxide and 1000 ppm azelaic acid in a 50/50 (weight ratio) formulation.

Example 14 was prepared from a blend of the propylene resin polymer of Control I and 2 ppm Q dye.

Table X shows the results of differential thermal analysis and X-ray diffraction measurement of Example 14 and Comparative Examples EK.

In Controls E and F, polypropylene homopolymer was blended with 1, 10 and 100 ppm of either terephthalic acid + CaO or azelaine + BaO. No increase in Tc value was observed for either nucleation system and only trace amounts of β crystallinity were detected in the second thermal scan. Two samples containing 100 ppm of either nucleating agent were compression molded into thin films and tested under orthogonal polars. Large α-type spherulites were seen, with only slight scattering of β-spherulites.

In another study, formulations were prepared using both 1000 ppm levels of different nucleating agents and propylene homopolymers and blends containing polypropylene homopolymers, ethylene / propylene block copolymers, low molecular weight polypropylene. did. As a control,
In the absence of nucleating agent, one sample prepared a formulation containing 2 ppm of Q dye. Since CaCO ₃ High levels already exists by filler particles, to prepare a one filling sample in the presence only azelaic acid. DS of these controls
C and X-ray data are shown in Table X.

According to the DSC data, the non-nucleated resin is 11
It has a Tc value of 5 to 116 ° C., indicating that none of the oxide / acid mixed nucleating agents showed a significant increase in this value. Only the sample with Q dye showed a large increase in Tc value and a large beta melting peak. X-ray data on the cast film showed that the presence of Q dye only gave a large increase in K value.

[0099]

[Table 10]

Front Page Continuation (72) Inventor Jessie Wu, Andalusia Court, Doleville, Georgia 30360, USA 4713 (56) References JP-A-60-262625 (JP, A) (58) Fields investigated (Int.Cl . ^7, DB name) B32B 1/00 - 35/00 C08J 5/18 C08L 23/10 - 23/16 WPI / L (QUESTEL)

Claims (3)

(57) [Claims] 1. A thermoformable sheet comprising one or more intermediate layers of a crystalline resin polymer of propylene having β-spherulites present at K values of 0.3 to 0.95 and two outer layers of thermoplastic resin. 2. The β-spherulite is included in the resin polymer by incorporating one or more suitable β-spherulite nucleating agents into the resin polymer prior to forming the sheet. Thermoformable sheet. 3. A microwave oven comprising one or more intermediate layers containing a crystalline resin polymer of propylene having α spherulites and a residue of an organic β spherulite nucleating agent, and two outer layers of a thermoplastic resin. Possible thermoformed articles.