JP2022137415A - Methacrylic resin composition for hot plate fusion, and use to hot plate fusion and fusion method - Google Patents

Abstract

To provide a methacrylic resin composition for hot plate fusion that is difficult to generate cobwebbing when separating a resin composition from a hot plate of hot plate fusion, and is difficult to generate a peel residue of the resin composition on a surface of a metal mold at the time of injection molding, that is, suitable for hot plate fusion and injection molding, and excellent in peeling ability from a hot plate or a mold.SOLUTION: A methacrylic resin composition for hot plate fusion, comprises, a (meth)acrylic polymer having a repeating unit derived from methyl methacrylate as a main component, and a fatty acid. Use of the methacrylic resin composition for hot plate fusion is also provided. A fusion method comprises a step of contacting at least a portion of a first member formed from the methacrylic resin composition for hot plate fusion with a hot plate to melt, and a step of separating the first member from the hot plate to crimp with the second member.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a methacrylic resin composition for hot plate welding, use for hot plate welding, and a welding method.

Due to its excellent appearance, transparency, weather resistance, chemical resistance, etc., methacrylic resins are used as vehicle parts such as tail lamp covers, head lamp covers, meter panels, and other vehicle interior and exterior materials; building materials; , bathtubs, flush toilets, and other housing equipment.
When a methacrylic resin is used for the above applications, such a member is joined to a member made of a styrene resin such as MS resin or ABS resin, or a resin other than methacrylic resin such as polycarbonate resin, and processed. be. A hot plate fusion method is known as a method for joining these members (Patent Documents 1 to 4).
In the hot plate fusion method, the joint surfaces of the above-mentioned members are heated and melted by closely contacting them with a metal hot plate, and after the hot plate is withdrawn, these are joined until the resin cools and solidifies. It is a method of joining by welding (crimping) with other members, and high welding strength can be obtained. In addition, the hot plate fusion method is capable of welding large parts together, and has the advantage of eliminating the time and effort required to apply adhesive and harden the adhesive. is an excellent method for

JP-A-2005-239823 JP 2009-249528 A WO2009-125766 JP 2009-249529 A

In the hot plate fusion method, by increasing the temperature of the hot plate, it is possible to melt the joint portions of the respective members in a short time. However, if the hot plate temperature is too high, a part of the resin may not be peeled off from the hot plate well when the members are separated from the hot plate, and a phenomenon of being stretched like a string (so-called stringing) may be observed. The appearance of the product is spoiled. Therefore, a method is used in which the temperature of the hot plate is lowered to the extent that the joined portion of the member can be melted and stringiness does not occur in the joined portion when the member is separated from the hot plate.
However, in the methacrylic resin compositions disclosed in Patent Documents 1 to 4, after being melted on the hot plate, when the resin is pulled away from the hot plate, part of the resin is not peeled off from the hot plate, causing stringiness. Also, when the molded article is separated from the mold during injection molding, a phenomenon in which resin remains on the surface of the mold (so-called peeling residue) may be observed. In such a case, there are problems such as the appearance of the product being damaged due to roughening of the joint surface of the parts, and unnecessary cleaning of the surface of the hot plate for hot plate fusion and the surface of the mold for injection molding. there were.

An object of the present invention is to solve these problems. That is, an object of the present invention is to reduce the occurrence of peeling residue of the resin composition on the mold surface during injection molding, and to reduce the occurrence of stringing when the resin composition is separated from the hot plate during hot plate fusion. The object of the present invention is to provide a methacrylic resin composition for hot plate welding suitable for hot plate welding.
Another object of the present invention is to provide a method of using the methacrylic resin composition for hot plate welding for hot plate welding.

The present inventors have reached the present invention as a result of repeated studies to solve the above problems.
That is, the first gist of the present invention resides in a methacrylic resin composition for hot plate welding, which contains a (meth)acrylic polymer having a repeating unit derived from methyl methacrylate as a main component, and a fatty acid.
A second gist of the present invention is the use of the methacrylic resin composition for hot plate welding for hot plate welding.
The third gist of the present invention is the first methacrylic resin composition for hot plate welding containing a (meth)acrylic polymer containing repeating units derived from methyl methacrylate as a main component, and a fatty acid. The fusion bonding method comprises the steps of bringing at least part of a member into contact with a hot plate to melt it, and separating the first member from the hot plate and press-bonding it to the second member.

According to the present invention, stringing is less likely to occur when the resin composition is separated from the hot plate during hot plate fusion, and peeling residue of the resin composition is less likely to occur on the mold surface during injection molding. It is possible to provide a methacrylic resin composition for hot plate welding suitable for hot plate welding.

It is process drawing which shows the hot plate fusion|bonding method which concerns on this embodiment. (a) A schematic side view of a disk-shaped molded product used for evaluation of releasability. (b) A schematic top view of a disk-shaped molded product used for evaluation of releasability. It is the schematic diagram which looked at the conical test piece used for stringiness evaluation from the side. FIG. 2 is a schematic diagram showing a state in which a conical test piece is stringy in a stringiness test.

Embodiments of the present invention will be described below.
As used herein, "(meth)acrylate" means at least one selected from "acrylate" and "methacrylate", and "(meth)acrylic acid" is selected from "acrylic acid" and "methacrylic acid". and "(meth)acrylic resin" means at least one selected from "acrylic resin" and "methacrylic resin".
In the present invention, "monomer" means an unpolymerized compound, and "repeating unit" means a unit derived from the monomer formed by polymerization of the monomer. The repeating units may be units directly formed by a polymerization reaction, or some of the units may be converted to another structure by treating the polymer.
In the present invention, "% by mass" indicates the content ratio of a given component contained in 100% by mass of the total amount.
In the present specification, the "obtained resin molded article" means a molded article obtained by molding the methacrylic resin composition for hot plate welding of the present invention.

The present invention will be described in detail below.

<Methacrylic resin composition for hot plate fusion>
The methacrylic resin composition for hot plate welding of the present invention (hereinafter referred to as "methacrylic resin composition" as appropriate) is a resin composition containing a (meth)acrylic polymer described later and a fatty acid described later.
When the methacrylic resin composition for hot plate welding of the present invention is used for hot plate welding, it can melt the joints of members, and when the members are separated from the hot plates, stringiness occurs at the joints. It is resistant to heat and is excellent as a material for hot plate welding.
Furthermore, the methacrylic resin composition for hot plate welding of the present invention is excellent in releasability from a mold when used for injection molding.

The melt flow rate (MFR) of the methacrylic resin composition for hot plate welding of the present invention is not particularly limited, but preferably conforms to ISO 1133-1:2011 at a temperature of 230° C. and a load of 3.8 kg. The MFR measured under the conditions of is preferably in the range of 0.1 to 10 g/10 min. 0.2 to 5.0 g/10 min or less is more preferable, and 0.3 to 2.0 g/10 min or less is even more preferable.
When the MFR is 10 g/10 min or less, the generation of air bubbles or the like is effectively suppressed when the methacrylic resin composition is melted in the hot plate fusion method. When the MFR is 0.1 g/10 min or more, the moldability of the methacrylic resin composition is improved.

In order to control the MFR to 0.1 to 10 g/10 min, it is possible to control the composition ratio of the monomer units as described above, or to adjust the weight average molecular weight of the (meth)acrylic polymer. etc. are valid.

<(Meth) acrylic polymer>
The (meth)acrylic polymer is one of the constituent components of the methacrylic resin composition for hot plate welding of the present invention.
The (meth)acrylic polymer in the present invention is a polymer mainly composed of repeating units derived from methyl methacrylate (hereinafter referred to as "methyl methacrylate units").
By containing the (meth)acrylic polymer, the methacrylic resin composition for hot plate welding of the present invention improves the transparency of the obtained resin molding and suppresses the thermal decomposition of the resin molding. , weather resistance and moldability can be improved.
In the present specification, "mainly composed of methyl methacrylate units" refers to containing 70% by mass or more of methyl methacrylate units with respect to 100% of the total mass of the (meth)acrylic polymer. .

In one embodiment of the (meth)acrylic polymer, the content of methyl methacrylate units in the (meth)acrylic polymer is relative to 100% of the total mass of the (meth)acrylic polymer. , 70% by mass or more. Specifically, the (meth)acrylic polymer is a homopolymer of methyl methacrylate, or a repeating unit derived from a methyl methacrylate unit of 70% by mass or more and less than 100% by mass, and a monomer other than methyl methacrylate. Copolymers containing more than 0% by mass and 30% by mass or less of units (hereinafter referred to as "other monomeric units") can be mentioned.

The "other monomer" used for the other monomer unit is not particularly limited as long as it is a monomer that can be copolymerized with methyl methacrylate, and can be radically polymerized in one molecule. It may be a monofunctional monomer having one double bond, or a polyfunctional monomer having two or more radically polymerizable double bonds in one molecule. Among them, acrylic acid esters are preferable from the viewpoint of excellent balance between fluidity, moldability and thermal decomposability of the (meth)acrylic polymer.

When an acrylic ester is used as the other monomer, the (meth)acrylic polymer contains 70% by mass of methyl methacrylate units with respect to 100% of the total mass of the (meth)acrylic polymer. It is preferable to contain more than 100% by mass and more than 0% by mass of the other monomer and 30% by mass or less, and the methyl methacrylate unit is 80% by mass or more and 99.9% by mass or less and other monomer units It is more preferable to contain 0.1% by mass or more and 20% by mass or less, and 90% by mass or more and 99.5% by mass or less of methyl methacrylate units and 0.5% by mass or more and 10% by mass or less of other monomer units. Containing is more preferable.

Examples of the acrylic acid ester include methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, and 2-hydroxyethyl acrylate. These acrylic acid esters may be used alone or in combination of two or more. Among these acrylates, methyl acrylate or ethyl acrylate is preferred.

Alternatively, as another embodiment of the (meth)acrylic polymer, the main chain includes a repeating unit derived from a (meth)acrylate monomer (hereinafter abbreviated as "(meth)acrylate unit" ) and a structural unit derived from a ring structure (hereinafter abbreviated as “ring structural unit”).
Examples of the ring structural unit include at least one selected from glutaric anhydride structural units, maleic anhydride structural units, glutarimide structural units, lactone ring structural units, and N-substituted maleimide structural units.

The lower limit of the content of the (meth)acrylic acid ester unit in the polymer (A) is not particularly limited, but the obtained resin molding is said to be excellent in transparency, processability, and mechanical properties. From the viewpoint of not impairing the original performance of the acrylic resin, the total number of moles of repeating units contained in the polymer (A) is preferably 80.0 mol%, more preferably 90.0 mol%, and 94.0 mol%. More preferred. On the other hand, the upper limit of the content of (meth)acrylic acid ester units in the (meth)acrylic polymer is not particularly limited, but from the viewpoint of excellent heat resistance of the obtained resin molding, 99.999 mol% Preferably, 99.9 mol % is preferred, and 99.5 mol % is more preferred. The above preferable upper limit and preferable lower limit can be arbitrarily combined.

The lower limit of the content ratio of the cyclic structural unit in the polymer (A) is not particularly limited, but from the viewpoint that the obtained resin molding has excellent heat resistance, the content of the repeating unit contained in the polymer (A) is 0.001 mol % is preferable, 0.01 mol % is more preferable, and 0.05 mol % is even more preferable with respect to the total number of moles. Although the upper limit of the content of the ring structural unit in the (meth)acrylic polymer is not particularly limited, it is preferably 10.0 mol% from the viewpoint of excellent heat resistance of the resulting resin molding, and suppression of molding coloring. , 3.0 mol% is more preferable, and 0.3 mol% is even more preferable, from the viewpoint of excellent molding appearance and weather resistance.
The above preferable upper limit and preferable lower limit can be arbitrarily combined.

Examples of the (meth)acrylic acid ester units include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, n-butyl (meth) acrylate, iso -butyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate ) acrylate, isobornyl (meth)acrylate, glycidyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, norbornyl (meth)acrylate, adamantyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate It is a structural unit derived from a monomer such as (meth)acrylate compounds such as acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and (meth)acrylic acid. One of these structural units may be used alone, or two or more thereof may be used in combination. A methyl methacrylate unit is preferable from the viewpoint of improving the thermal stability of the obtained resin molding.

The (meth)acrylic acid ester unit can contain a structural unit derived from a monomer having a carboxylic acid group (hereinafter abbreviated as "monomer unit having a carboxylic acid group"). A monomer unit having a carboxylic acid group forms a cyclic structural unit through a cyclization reaction, so that the cyclic structural unit can be introduced into the main chain of the (meth)acrylic polymer. Therefore, the (meth)acrylic polymer may contain a monomer unit having an unreacted carboxylic acid group. Examples of monomers having a carboxylic acid group include acrylic acid, methacrylic acid, 2-(hydroxymethyl)acrylic acid, 2-(hydroxyethyl)acrylic acid, crotonic acid and the like. These other monomers may be used singly or in combination of two or more.

As one aspect of the polymer (A), the (meth)acrylic acid ester unit is a repeating unit (A1) derived from methyl methacrylate (hereinafter abbreviated as "unit (A1)") and (meth) Repeating units (A2) derived from acrylic acid (hereinafter abbreviated as "units (A2)"), and glutaric anhydride structural units (A3) as the ring structural units (hereinafter abbreviated as "units (A3)") abbreviated).

The unit (A3) is a structural unit represented by the following chemical structural formula.

［式中、Ｒ^Ａ及びＲ^Ｂは、それぞれ独立に、水素原子またはメチル基を示す。］

[In the formula, ^RA and ^RB each independently represent a hydrogen atom or a methyl group. ]

By including the unit (A3) in the polymer (A), the heat resistance of the obtained resin molding can be improved.

The lower limit of the content ratio of the unit (A1) in the polymer (A) is not particularly limited, but the obtained resin molding has excellent transparency, workability, and mechanical properties. From the viewpoint of not impairing the performance of the polymer (A), the total number of moles (100 mol%) of the repeating units contained in the polymer (A) is preferably 80.0 mol%, more preferably 90.0 mol%, and 94.0 mol%. More preferred. The upper limit of the content of the units (A1) in the polymer (A) is not particularly limited, but from the viewpoint of excellent heat resistance of the obtained resin molded product, it is preferably 99.499 mol%, more preferably 99.0 mol%. is more preferred, and 98.0 mol % is even more preferred.
The above preferable upper limit and preferable lower limit can be arbitrarily combined.

(Meth)acrylic acid constituting the unit (A2) refers to acrylic acid, methacrylic acid, or a mixture thereof. Methacrylic acid is preferred because the obtained resin molding has excellent heat resistance.

The lower limit of the content of the units (A2) in the polymer (A) is the total moles of the repeating units contained in the polymer (A), from the viewpoint of excellent heat resistance and mechanical properties of the resulting resin molding. 0.5 mol % is preferred, 1.0 mol % is more preferred, and 2.0 mol % is even more preferred with respect to the number. The upper limit of the content ratio of the unit (A2) in the polymer (A) is, from the viewpoint of not impairing the original performance of the acrylic resin such as excellent molding appearance, low water absorption, and moldability of the obtained resin molding, 20.0 mol % is preferred, 7.0 mol % is more preferred, and 3.5 mol % is even more preferred.
The above preferable upper limit and preferable lower limit can be arbitrarily combined.

The lower limit of the content ratio of the units (A3) in the polymer (A) is the total number of moles of the repeating units contained in the polymer (A), from the viewpoint that the obtained resin molding has excellent heat resistance. , is preferably 0.001 mol %, more preferably 0.01 mol %, even more preferably 0.05 mol %. The upper limit of the content of the unit (A3) in the polymer (A) is preferably 10.0 mol% from the viewpoint of suppressing molding coloration of the obtained resin molding, molding appearance, and excellent weather resistance. 0 mol % is more preferred, and 0.3 mol % is even more preferred.
The above preferable upper limit and preferable lower limit can be arbitrarily combined. For example, the content of the units (A3) in the polymer (A) is 0.001 mol% or more and 10.0 mol% or less with respect to the total number of moles of repeating units contained in the polymer (A), and 0 01 mol % or more and 2.0 mol % or less is preferable, and 0.3 mol % or more and 0.15 mol % or less is more preferable.

The unit (A3) is a methoxycarbonyl group derived from the unit (A1) and a unit (A2) adjacent to the unit (A1) in a copolymer obtained by copolymerizing methyl methacrylate and (meth)acrylic acid. It may be a unit constructed by a cyclization reaction with a carboxyl group derived from.

In this specification, the content of each unit in the polymer including the unit (A1), the unit (A2) and the unit (A3) is a value calculated from ¹ H-NMR measurement. Specifically, the method disclosed in WO2019/013186 can be used.

In addition, the method for producing a polymer containing units (A1), units (A2) and units (A3) is not particularly limited, but for example, the production disclosed in WO2017-022393 and WO2019/013186 method can be used.

Although the weight average molecular weight of the (meth)acrylic polymer is not particularly limited, it is preferably from 50,000 to 150,000. 70,000 or more and 130,000 or less are preferable. When the (meth)acrylic polymer has a mass average molecular weight of 50,000 or more, the mechanical properties of the obtained resin molding are excellent. Moreover, when the mass average molecular weight of the (meth)acrylic polymer is 150,000 or less, the fluidity of the methacrylic resin composition for hot plate welding is excellent.
In this specification, the weight average molecular weight is a value measured by gel permeation chromatography using standard polystyrene as a standard sample.
In order to control the weight average molecular weight of the (meth)acrylic polymer, it is preferable to adjust the amount of the chain transfer agent in the polymerization of the monomer mixture.

The method for producing the (meth)acrylic polymer is not particularly limited, and examples thereof include a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method, and a solution polymerization method. Among these polymerization methods, the bulk polymerization method and the suspension polymerization method are preferable from the viewpoint of excellent productivity.

<Fatty acid>
Fatty acid is one of the constituent components of the methacrylic resin composition for hot plate bonding of the present invention.
The fatty acid in the present invention improves the releasability from the mold during injection molding, makes it difficult for the resin composition to leave a peeling residue on the mold surface, and also removes the resin composition from the hot plate during hot plate fusion. This component is added to prevent stringing from occurring when separating. That is, the fatty acid in the present invention is a component for improving the releasability of the resin composition from the mold for injection molding, and also for improving the releasability during hot plate fusion bonding. be.

Fatty acids in the present invention include chain hydrocarbon compounds having at least one carboxyl group in the molecule. A chain hydrocarbon compound having at least one carboxyl group in the molecule means a compound in which the carbon atom to which the carboxyl group is bonded is a constituent atom of the carbon chain. The carbon chain in the chain hydrocarbon compound having at least one carboxyl group in the molecule may be saturated or unsaturated, and may be linear or branched. good too.
Among the fatty acids, chain hydrocarbon compounds having one carboxyl group are preferred. When the number of carboxyl groups is one, no increase in molecular weight due to cross-linking reaction with the reactive functional group of the (meth)acrylic polymer occurs during melt-kneading or melt-molding, and flowability does not decrease.

Furthermore, by selecting the 10% weight loss temperature and/or the melting point of the fatty acid, the methacrylic resin composition for hot plate welding of the present invention can be released from a mold when injection molded, or the obtained It is possible to improve the releasability from the hot plate when the resin molding is hot-plate fused.

The upper limit of the 10% weight loss temperature of the fatty acid is determined from the viewpoint of improving the releasability from the mold during injection molding and the releasability from the hot plate during hot plate fusion of the obtained resin molded product. 250° C. or less is preferable. The reason for this is not clear, but if the 10% weight loss temperature is 250° C. or less, the fatty acid contained in the resin molded body is localized in the melted portion during hot plate fusion, making stringing less likely to occur. In addition, during injection molding, the fatty acid contained in the methacrylic resin composition easily volatilizes in the mold, and as a result, the methacrylic resin composition injected into the mold later adheres to the mold surface. It is presumed that the fatty acid liquefied or condensed as a result of the diffusion and migration of the fatty acid causes a high content of the fatty acid to exist on the surface and in the vicinity of the surface of the finally obtained resin molding. The 10% weight loss temperature of the fatty acid is more preferably 240°C or lower, and even more preferably 230°C or lower.
On the other hand, the lower limit of the 10% weight loss temperature of the fatty acid is from the standpoint that the releasability from the mold during injection molding and the releasability from the hot plate during hot plate fusion bonding of the obtained resin molding are improved. Therefore, 150° C. or higher is preferable. Although the reason for this is not clear, if the 10% weight loss temperature is 150° C. or higher, the fatty acid excessively volatilizes from the resin molding during hot plate fusion bonding, resulting in a decrease in hot plate releasability. In addition, during injection molding, the fatty acid volatilized in the mold adheres to the mold surface and tends to be liquefied or condensed, and as a result, the fatty acid is discharged as gas from the gas vent of the mold. It is speculated that this is because the amount of fatty acid is suppressed from decreasing, and a high content of fatty acid can be present on the surface and in the vicinity of the surface of the obtained resin molded product. The 10% weight loss temperature of the fatty acid is more preferably 170°C or higher, more preferably 200°C or higher.
The preferred upper and lower limits of the 10% weight loss temperature of the above fatty acids can be combined arbitrarily. For example, the 10% weight loss temperature of fatty acids is preferably 150° C. or higher and 250° C. or lower, more preferably 170° C. or higher and 240° C. or lower, and even more preferably 200° C. or higher and 230° C. or lower.

The lower limit of the melting point of the fatty acid is set from the viewpoint of improving the releasability from the mold during injection molding and further improving the releasability from the hot plate during hot plate fusion bonding of the obtained resin molded product. , 50° C. or higher. The reason for this is not clear, but if the melting point of the fatty acid is 50° C. or higher, the decrease in the viscosity of the methacrylic resin composition during hot plate fusion can be suppressed, so stringing is less likely to occur, and the methacrylic resin The fatty acid contained in the composition tends to diffuse in the molten resin when the resin is filled into the mold during injection molding. It is presumed that the fatty acid that adheres to the surface of the mold and liquefies or condenses diffuses and migrates, resulting in a high content of fatty acids on the surface and near the surface of the finally obtained resin molded product. . The melting point of the fatty acid is more preferably 55°C or higher, more preferably 60°C or higher.
On the other hand, the upper limit of the melting point of the fatty acid is preferably 100° C. or less from the viewpoint that the obtained resin molded product can be easily removed from the hot plate. The reason for this is not clear, but if the melting point of the fatty acid is 100° C. or less, the effect of suppressing the stringing of the fatty acid in the resin molding during hot plate fusion is likely to be obtained. It is speculated that the fatty acid volatilized in the mold liquefies or condenses on the mold surface, facilitating the formation of a film layer composed of the fatty acid on the mold surface, and as a result, the above-described effects and effects can be easily obtained. is doing. The melting point of the fatty acid is more preferably 90°C or lower, more preferably 80°C or lower.
The preferred upper and lower limits of the melting points of the above fatty acids can be combined arbitrarily. For example, the melting point of the fatty acid is preferably 50° C. or higher and 100° C. or lower, more preferably 55° C. or higher and 90° C. or lower, and even more preferably 60° C. or higher and 80° C. or lower.

Although the molecular weight of the fatty acid is not particularly limited, fatty acids having a molecular weight of 100 or more and 500 or less can be preferably used. A molecular weight of 200 or more and 400 or less is more preferable. When the molecular weight of the fatty acid is 100 or more, the volatility of the fatty acid is low, so it is sufficient to improve the releasability from the mold during injection molding and the releasability from the hot plate during hot plate fusion. effect is obtained. On the other hand, when the molecular weight of the fatty acid is 500 or less, the compatibility with the (meth)acrylic polymer is high, so that it is easy to separate from the mold during injection molding and from the hot plate during hot plate fusion. Moldability is excellent, and since less fatty acid remains on the surface of the hot plate and the mold when the mold is released, the surface of the hot plate and the mold is less likely to be stained, and the obtained resin molding is less likely to be cloudy.

The number of carbon atoms in the fatty acid is not particularly limited, but fatty acids having 10 to 22 carbon atoms can be preferably used. When the number of carbon atoms is 10 or more, the volatility of the fatty acid is low, so it is sufficient to improve the releasability from the mold during injection molding and the releasability from the hot plate during hot plate fusion. effect is obtained. On the other hand, when the number of carbon atoms is 22 or less, the compatibility with the (meth)acrylic polymer is high, so the releasability from the mold and the hot plate are excellent. Since the amount of fatty acid remaining on the surface of the mold is reduced, the surface of the hot plate and the mold is less likely to be stained, and the obtained resin molding is less likely to be fogged.

Specific examples of the fatty acids include saturated fatty acids such as lauric acid, palmitic acid, stearic acid, myristic acid and behenic acid, and unsaturated fatty acids such as oleic acid and linoleic acid. These fatty acids may be used individually by 1 type, and may use 2 or more types together. Among these fatty acids, stearic acid, palmitic acid and myristic acid are preferred.

The content of the fatty acid in the methacrylic resin composition for hot plate welding is not particularly limited, but is preferably 0.01 part by mass with respect to 100 parts by mass of the (meth)acrylic polymer. Above 1.0 parts by mass can be made below. 0.1 parts by mass or more and 0.3 parts by mass or less is more preferable. When the content of the fatty acid is more than 0.01 part by mass, the releasability from the mold during injection molding and the releasability from the hot plate during hot plate fusion are improved. If the amount is less than the part, less fatty acid remains on the surfaces of the hot plate and the mold when the mold is released, so that the surface of the hot plate and the mold is less likely to be stained, and the resulting resin molding is less likely to be fogged.

The content of the fatty acid in the methacrylic resin composition for hot plate welding is not particularly limited, but is preferably 0.00% per 100% of the total mass of the methacrylic resin composition for hot plate welding. 01% by mass or more and 1.0% by mass or less. 0.1% by mass or more and 0.3% by mass or less is more preferable. When the content of the fatty acid is more than 0.01% by mass, the releasability from the mold during injection molding and the releasability from the hot plate during hot plate fusion are improved. %, less fatty acid remains on the surface of the hot plate and the mold when the mold is released, so that the surface of the hot plate and the mold is less likely to be stained, and the obtained resin molding is less likely to be fogged.

<Other additives>
The methacrylic resin composition for hot plate welding of the present invention may optionally contain an ultraviolet absorber, a light diffusing agent, an antioxidant, a coloring agent, a pigment, and so on within a range that does not affect the effects of the present invention. Thermal stabilizers, reinforcing agents, fillers, flame retardants, foaming agents, lubricants, plasticizers, antistatic agents and the like may be incorporated.

<Method for producing methacrylic resin composition for hot plate welding>
Examples of the method for producing the methacrylic resin composition for hot plate welding of the present invention include the following methods (1) and (2).
(1) A method of charging the (meth)acrylic polymer and the fatty acid into a single extruder or a twin-screw extruder, heating and melting them, and kneading them to mix them.
(2) A method of polymerizing a monomer containing methyl methacrylate as a main component by mixing the fatty acid.

The methacrylic resin composition for hot plate welding of the present invention can be obtained by the production method described above.
The methacrylic resin composition for hot plate welding of the present invention is less likely to leave a peeling residue of the resin composition on the mold surface during injection molding. In addition, stringing is less likely to occur when the resin composition is separated from the hot plate for hot plate fusion. Therefore, the resin molding obtained by injection molding the methacrylic resin composition for hot plate welding of the present invention can be suitably used as a member for hot plate welding.

<fusion method>
The fusion bonding method of the present invention includes the steps of bringing at least a part of the first member formed of the methacrylic resin composition for hot plate fusion into contact with a hot plate to melt the first member, and pulling away from and crimping with a second member.
Here, the material of the second member is not particularly limited as long as it is heat-sealable with the (meth)acrylic polymer. Examples include styrene-based resins such as ABS, SAN, AS, and MS resins, polycarbonate-based resins, and polyvinyl chloride-based resins. Also, the second member can use the methacrylic resin composition for hot plate welding according to the present invention.

FIG. 1 is a process chart showing one embodiment of the fusion bonding method of the present invention.
A hot plate 3 is placed between the first member 1 and the second member 2 (FIG. 1(a)), and at least a part of the first member 1 and the second member 2 is brought into contact with the hot plate 3. 1(b)), separated from the hot plate 4 (FIG. 1(c)), and melted portion 1a of the first member and melted portion 2a of the second member are fused together. (Crimping), the first member 1 and the second member 2 can be joined (FIG. 1(d)).

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples.

[Releasability during injection molding]
As an index of releasability during injection molding, the ejector pin pressure was measured by the following method.
The pellet-shaped methacrylic resin compositions obtained in Examples and Comparative Examples were dried with hot air at 80 ° C. for about 16 hours, and then an injection molding machine (model name: EC75-SXII, Shibaura Kikai) set at a cylinder temperature of 260 ° C. (manufactured by Co., Ltd.), and a mold (a vertical diameter of 75 mm and a thickness of 3 mm (4 in FIG. 2) in the shape of a disk provided with a gas release portion can be molded. The center of this disk-shaped mold There is a gate part in the mold.Ejection pins for releasing the molded product are arranged one in the center of the disk-shaped mold and four in the peripheral part of the mold at equal intervals.) Continuous molding is performed under the conditions of a mold temperature of 90 ° C and an injection pressure of 80 MPa, and a pressure sensor installed on the back of the ejector pin in the center part detects the ejector pin when releasing the molded product ( 4 ) from the mold. Pressure (unit: MPa) was measured. The lower the ejector pin pressure value, the better the releasability.

[Molding appearance after injection molding]
As an index of molded appearance after injection molding, the presence or absence of poor peeling was observed by the following method.
A disc-shaped molded product (4) was continuously molded for 40 shots in the same manner as the evaluation of releasability. The surface of the obtained molded product (4) was visually observed, and when even one shot of surface roughness due to poor peeling from the mold was observed on the surface of the molded product (4), it was determined to be defective in peeling.

[Releasability during hot plate fusion]
As an index of releasability during hot plate fusion, stringiness was observed by the following method.
- Test piece preparation: The sprue portion (5) was cut from the disk-shaped molded product (4) (vertical diameter 75 mm, thickness 3 mm) molded for mold release evaluation, and a conical test piece (6) ( 10 mm in bottom diameter and 70 mm in height) were fabricated (see FIGS. 2 and 3).
Hot plate: A plate made of SUS304 was placed on the hot plate (7), and this was used as the hot plate (8). The temperature of the hot plate surface was controlled by actually measuring the surface temperature of the hot plate (8) with a probe thermometer.
-Test method: After heating the surface temperature of the hot plate (8) to 260 ° C., the bottom part (9) (diameter 10 mm) of the conical test piece (6) was placed on the surface of the hot plate (8). for 20 seconds to melt the contact area, then lift the test piece (6) up to a height of 30 cm to check for stringing between the test piece (6) and the hot plate (8). (See Figure 4). Stringing is part of the thread-like methacrylic resin composition. Five test pieces were prepared, the above operation was performed once for each test piece, and evaluation was made according to the following criteria.
(criterion)
〇: 0 times with stringing △: 1-2 times with stringing ×: 3-5 times with stringing

<Melting point>
The melting points of fatty acids were evaluated by the following method using a differential scanning calorimeter (DSC) (manufactured by Seiko Instruments Inc., model: DSC-6200).
About 10 mg of fatty acid is placed in an aluminum sample container, heated to 200° C. at a temperature increase rate of 10° C./min, held for 5 minutes to melt, and then cooled to 0° C. at 10° C./min. The temperature was again raised at a temperature elevation rate of 10°C/min, held for 5 minutes, and then lowered at 10°C/min.

<10% Weight Loss Temperature>
The 10% weight loss temperature of fatty acids was measured using a thermogravimetric analyzer (TGA) (manufactured by Seiko Instruments Inc., model: TG/DTA6200) according to the following method.
While flowing dry nitrogen at 100 ml/min, the temperature was raised from 40° C. to 500° C. at a heating rate of 10° C./min, and the temperature at which the weight reduction rate was 10% (10% by mass reduction) was measured.

(raw materials)
Abbreviations of compounds used in Examples and Comparative Examples are as follows.
MMA: Methyl methacrylate (trade name: Acryester (registered trademark) M, manufactured by Mitsubishi Chemical Corporation)
MA: Methyl acrylate (manufactured by Mitsubishi Chemical Corporation)
MAA: methacrylic acid Polymerization initiator (1): 2,2'-azobis (2-methylpropionamidine) dihydrochloride Polymerization initiator (2): 2,2'-azobis-2-methylbutyronitrile (trade name : V-59, manufactured by Wako Pure Chemical Industries, Ltd.)
Chain transfer agent (1): n-octyl mercaptan (manufactured by Tokyo Chemical Industry Co., Ltd.)
Polymer (1): ACRYPET (registered trademark) VH (trade name, manufactured by Mitsubishi Chemical Corporation, acrylic resin containing 98% by mass of methyl methacrylate units)
Polymer (2): The (meth)acrylic polymer produced in Production Example 1 Fatty acid compound (B-1): Myristic acid (trade name: LUNAC MY-98, manufactured by Kao Corporation)
Fatty acid compound (B-2): palmitic acid (trade name: LUNAC P-95, manufactured by Kao Corporation)
Fatty acid compound (B-3): stearic acid (trade name: Lunax S-98, manufactured by Kao Corporation)
Fatty acid compound (B-4): myristyl alcohol (trade name: Calcol 4098, manufactured by Kao Corporation)
Fatty acid compound (B-5): cetyl alcohol (trade name: Calcol 6098, manufactured by Kao Corporation)
Fatty acid compound (B-6): stearyl alcohol (trade name: Calcol 8098, manufactured by Kao Corporation)
Fatty acid compound (B-7): glycerin monostearate (trade name: Rikemar S100A, manufactured by Riken Vitamin Co., Ltd.)
Fatty acid compound (B-8): glycerin mono-distearate (trade name: Rikemar S200A, manufactured by Riken Vitamin Co., Ltd.)
Fatty acid compound (B-9): stearyl stearate (trade name: Rikemar SL-900A, manufactured by Riken Vitamin Co., Ltd.)
Fatty acid compound (B-10): stearic acid amide (trade name: fatty acid amide S, manufactured by Kao Corporation)

Here, "containing as a main component" means containing 70% by mass or more of the target component with respect to the total mass (100% by mass) of fatty acids.

[Production Example 1]
900 parts by mass of deionized water, 60 parts by mass of 2-sulfoethylsodium methacrylate, 10 parts by mass of potassium methacrylate and 12 parts by mass of MMA were added to a reaction vessel equipped with a reflux condenser whose interior was replaced with nitrogen, and then the reaction was carried out with stirring. The temperature of the liquid in the container was raised to 50°C. After that, 0.08 part by mass of polymerization initiator (1) was added, and the liquid temperature in the reaction vessel was raised to 60° C. while stirring, and then 0.24 part by mass of MMA was added using a dropping pump. /min over a period of 75 minutes. After that, polymerization was carried out by holding for another 6 hours to obtain a dispersant (solid content: 10% by mass).

2000 parts by mass of deionized water and 4.2 parts by mass of sodium sulfate were added to a reaction vessel equipped with a nitrogen gas inlet tube and equipped with a reflux condenser, followed by stirring at a stirring speed of 320 rpm for 15 minutes. After that, a mixed solution of 1351.6 parts by mass of MMA, 36.3 parts by mass of MAA, 12.1 parts by mass of MA, 2.8 parts by mass of polymerization initiator (2) and 4.2 parts by mass of chain transfer agent (1) was added to a reaction vessel. and stirred for 5 minutes. Then, 6.72 parts by mass of the dispersant (solid content: 10% by mass) produced in Production Example 1 was added to the reaction vessel and stirred to disperse the monomer composition in the reaction vessel in water. After that, the inside of the reaction vessel was replaced with nitrogen.

Then, after the temperature of the liquid in the reaction vessel was raised to 75° C., the temperature of the liquid in the reaction vessel was continuously measured and kept at 75° C. until the polymerization exothermic peak was observed. After the polymerization exothermic peak was observed, the temperature of the liquid in the reaction vessel was raised to 90° C., and the mixture was held for 60 minutes to carry out polymerization. After that, the mixture in the reaction vessel is filtered, and the filtrate is washed with deionized water and dried at 80° C. for 16 hours to obtain a bead-like copolymer, which is used as a methacrylic resin precursor (copolymer). A combined precursor (1)) was obtained.
The composition of the copolymer precursor (1) was analyzed according to the above-described measurement method for the "content of units (A), (B) and (C)", and found to be 96.0 mol% of MMA units and methacrylic acid. 3.0 mol % of repeating units (hereinafter referred to as "MAA units") derived from methyl acrylate and 1.0 mol % of repeating units (hereinafter referred to as "MA units") derived from methyl acrylate.

Copolymer precursor (1) is supplied to a twin-screw extruder (model name “PCM30”, manufactured by Ikegai Co., Ltd.) and kneaded at 250° C. to obtain a pellet-shaped (meth)acrylic polymer, This was designated as polymer (2).
The composition of the obtained polymer (2) was 97.00 mol % of MMA units, 2.99 mol % of (meth)acrylic acid units, and 0.01 mol % of glutaric anhydride structural units. The (meth)acrylic acid unit means a repeating unit including the MAA unit and the MA unit.

[Example 1]
100 parts by mass of polymer (1) and 0.1 part by mass of fatty acid compound (B-1) as fatty acid are supplied to a twin-screw extruder (model name “TEM35”, manufactured by Shibaura Machine Co., Ltd.), and the extruder Melt-kneading was carried out at a cylinder temperature of 250°C, and a pellet-shaped methacrylic resin composition was obtained at a mold temperature of 60°C.
Table 1 shows the evaluation results of the obtained methacrylic resin composition.

[Reference example 1]
A methacrylic resin composition in the form of pellets was obtained in the same manner as in Example 1, except that no fatty acid was used. Table 1 shows the evaluation results of the obtained methacrylic resin composition.

[Examples 2-3, Comparative Examples 1-7]
A methacrylic resin composition in the form of pellets was obtained in the same manner as in Example 1, except that the type of fatty acid compound was changed. Table 1 shows the evaluation results of the obtained methacrylic resin composition.

[Example 4, Comparative Examples 8 to 9]
A methacrylic resin composition in the form of pellets was obtained in the same manner as in Example 1, except that the polymer (2) was used instead of the polymer (1) and the type and amount of the fatty acid compound added were changed. rice field. Table 1 shows the evaluation results of the obtained methacrylic resin composition.

The resin moldings of Examples 1 to 4 were excellent in releasability during injection molding and releasability during hot plate fusion bonding.
Since the resin molded product of Reference Example 1 did not contain fatty acid, it was inferior in releasability during injection molding and during hot plate fusion bonding.
Although the resin moldings of Comparative Examples 1 to 9 contained a fatty acid compound, they were inferior in releasability during injection molding and during hot plate fusion because no fatty acid was used.

The methacrylic resin composition for hot plate welding of the present invention is excellent in releasability from a mold during injection molding, and is excellent in releasability from a hot plate during hot plate fusion. Therefore, the molded article containing the methacrylic resin composition for hot plate welding of the present invention can be used as a vehicle member such as a tail lamp cover, a head lamp cover, and a meter panel such as a vehicle interior and exterior material; a building member; It can be suitably used as a raw material for housing equipment members such as flush toilets, and is particularly suitable as a raw material for vehicle members.

Vehicle parts include, for example, tail lamp covers, head lamp covers, meter panels, door mirror housings, pillar covers (sash covers), license garnishes, front grills, fog garnishes, and emblems.

REFERENCE SIGNS LIST 1 first member 1a melted portion of first member 2 second member 2a melted portion of second member 3 hot plate 4 disk-shaped molding 5 sprue portion 6 conical test piece 7 hot plate 8 hot plate 9 Bottom part 10 Stringing generated between the test piece and the hot plate

Claims (15)

A methacrylic resin composition for hot plate welding, comprising a (meth)acrylic polymer having a repeating unit derived from methyl methacrylate as a main component, and a fatty acid. The methacrylic resin composition for hot plate welding according to claim 1, wherein the fatty acid has a 10% weight loss temperature of 250°C or less. The methacrylic resin composition for hot plate welding according to claim 1 or 2, wherein the fatty acid has a melting point of 50°C or higher. 4. The methacrylic resin composition for hot plate welding according to claim 1, wherein the fatty acid is a chain hydrocarbon compound having at least one carboxyl group in the molecule. The methacrylic resin composition for hot plate welding according to any one of claims 1 to 4, wherein the fatty acid has a molecular weight of 100 or more and 500 or less. The content of the fatty acid is 0.01 parts by mass or more and 1.0 parts by mass or less with respect to 100 parts by mass of the (meth)acrylic polymer, according to any one of claims 1 to 5. A methacrylic resin composition for hot plate welding. 7. The content of the fatty acid is 0.01% by mass or more and 1.0% by mass or less with respect to 100% of the total mass of the methacrylic resin composition for hot plate welding. 4. The methacrylic resin composition for hot plate welding according to the above item. The methacrylic resin composition for hot plate welding according to any one of claims 1 to 7, wherein the fatty acid contains at least one selected from stearic acid, palmitic acid, and myristic acid. The methacrylic resin composition for hot plate welding according to any one of claims 1 to 8, wherein the content of repeating units derived from methyl methacrylate in the (meth)acrylic polymer is 70% by mass or more. . The (meth)acrylic polymer is a polymer (A) containing a repeating unit derived from a (meth)acrylate monomer and a structural unit derived from a ring structure,
wherein the structural unit derived from the ring structure comprises at least one selected from a glutaric anhydride structural unit, a maleic anhydride structural unit, a glutarimide structural unit, a lactone ring structural unit, and an N-substituted maleimide structural unit; Item 10. The methacrylic resin composition for hot plate welding according to any one of Items 1 to 9. 11. The polymer (A) according to claim 10, wherein the polymer (A) comprises a repeating unit (A1) derived from methyl methacrylate, a repeating unit (A2) derived from (meth)acrylic acid and a glutaric anhydride structural unit (A3). A methacrylic resin composition for hot plate welding. The methacrylic resin composition for hot plate welding according to any one of claims 1 to 11, which is used as a raw material for vehicle members. 13. The methacrylic resin composition for hot plate bonding according to claim 12, wherein the vehicle member is at least one selected from a tail lamp cover, a head lamp cover and a meter panel. Use of the methacrylic resin composition for hot plate welding according to any one of claims 1 to 13 for hot plate welding. a step of bringing at least part of the first member formed from the methacrylic resin composition for hot plate welding according to any one of claims 1 to 13 into contact with a hot plate to melt the first member;
pulling the first member away from the hot plate and crimping it with a second member;
A fusing method comprising:

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