JP6214989B2 - Acrylic resin foam and manufacturing method thereof - Google Patents

Description

  The present invention relates to an acrylic resin foam and a method for producing the same.

Conventionally, an acrylic resin foam (hereinafter also referred to as “foam”) has excellent strength, light weight, and excellent heat insulation properties. Therefore, by attaching fiber reinforced plastics (FRP) to the surface, It is used as a member for constituting a wall material of a cold storage room of a cargo vehicle, a hull of a small boat, a blade of wind power generation, an X-ray machine table for transmitting X-rays, and the like.
Such an acrylic resin foam is usually produced by preparing a polymerizable solution in which urea as a foaming agent and a radical polymerization initiator are mixed with an acrylic monomer, as shown in Patent Document 1 below. After pouring a polymerizable solution into a mold and heating the mold together to polymerize the acrylic monomer, the resulting foamable polymer is further heated to a high temperature to decompose urea and cause gas foaming. This method is adopted.

JP 2006-045256 A

However, the conventional acrylic resin foam has a problem that the variation of the bubble diameter becomes large.
For example, when an X-ray camera stand is made of an acrylic resin foam having a large variation in bubble diameter, relatively large bubbles may appear as shadows on a photograph taken with the X-ray camera.
Further, if the variation in the cell diameter of the acrylic resin foam is large, the aesthetics of the product made of the acrylic resin foam may be impaired, and the product value may be reduced.

  In view of the above problems, an object of the present invention is to provide an acrylic resin foam having a small variation in bubble diameter.

  The present inventors have intensively studied to solve the above problems, and found that an acrylic resin foam having a calcium concentration and a sodium concentration within a predetermined range is likely to have a small variation in cell diameter, The present invention has been completed.

That is, the present invention contains calcium and sodium,
In the acrylic resin foam, the calcium concentration is 2 to 150 μg / g, and the sodium concentration is 2 to 50 μg / g.

Further, the present invention provides a polymerizable solution containing a polymerizable monomer containing an acrylic monomer, a foaming agent containing a pyrolytic foaming agent, and a polymerization initiator, and after polymerizing the polymerizable monomer , Including a step of producing an acrylic resin foam by foaming the foamable polymer obtained by the polymerization,
Acrylic resin foam characterized by producing said acrylic resin foam containing calcium and sodium, having a calcium concentration of 2 to 150 μg / g and a sodium concentration of 2 to 50 μg / g It is in the manufacturing method of the body.

  ADVANTAGE OF THE INVENTION According to this invention, the acrylic resin foam which becomes easy to become a thing with small variation in a bubble diameter can be provided.

  Embodiments of the present invention will be described below.

First, the manufacturing method of the acrylic resin foam of this embodiment is demonstrated.
The manufacturing method of the acrylic resin foam of this embodiment produces a polymerizable solution containing a polymerizable monomer containing an acrylic monomer, a foaming agent containing a pyrolytic foaming agent, and a polymerization initiator.
Next, the polymerizable monomer is polymerized by heating the polymerizable solution to produce a foamable polymer (hereinafter also referred to as a foamable polymer production step). Then, the foamable polymer is foamed to contain calcium and sodium, the concentration of the calcium is 2 to 150 μg / g, and the concentration of the sodium is 2 to 50 μg / g. A body is produced (hereinafter also referred to as a foam production process).
Hereinafter, the components of the polymerizable solution will be described.

(Acrylic monomer)
Examples of the acrylic monomers include maleic anhydride, methacrylamide, (meth) acrylic acid, methyl methacrylate, maleic acid, fumaric acid, itaconic acid, itaconic anhydride, crotonic acid, methyl acrylate, and ethyl (meth) acrylate. , (Butyl) (meth) acrylate, lauryl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, acrylamide, maleic acid amide, maleic acid imide, etc. It is done.
In this specification, the term “(meth) acryl” means either “methacryl” or “acryl”.
In addition, when urea is used as a foaming agent to be described later, the acrylic monomer preferably contains a water-soluble acrylic monomer because it exhibits excellent solubility in urea, and contains (meth) acrylic acid. It is preferable to make it.
Furthermore, it is preferable to contain methyl methacrylate in the acrylic monomer in that it can exhibit excellent foamability when foaming the foamable polymer of the acrylic monomer.
Moreover, as said acrylic monomer, it is preferable to contain maleic anhydride and methacrylamide in the point which can provide high heat resistance to the acrylic resin foam obtained.

(Polymerizable monomer other than acrylic monomer)
In addition, as a polymerizable monomer other than the acrylic monomer, a monomer copolymerizable with the acrylic monomer may be contained in a small amount in the polymerizable solution for the purpose of modifying the acrylic resin foam.
In particular, it is preferable to contain a styrene monomer effective for improving foamability in the polymerizable solution.
However, if the styrene monomer is contained excessively, the hardness may be impaired, so the content of the styrene monomer in the polymerizable monomer is preferably 30% by mass or less.

More specifically, the polymerizable solution in the present embodiment includes 50 to 70% by mass of methyl methacrylate, 14 to 30% by mass of (meth) acrylic acid, It is preferable that 20% by mass is styrene.
An acrylic resin foam produced using such a polymerizable solution has an advantage of being excellent in compressive strength.
In addition, all (meth) acrylic acid contained in the ratio of 14-30 mass% may be methacrylic acid, all may be acrylic acid, and both methacrylic acid and acrylic acid are combined. You may make it contain in a polymeric solution so that it may become the mass%.
However, when urea is used as a foaming agent to be described later, it is preferable to contain a large amount of methacrylic acid from the viewpoint of solubility in urea.

(Foaming agent)
As the foaming agent, a foaming agent containing a pyrolytic foaming agent is used.
The pyrolyzable foaming agent decomposes at 65 ° C. or higher to generate gas, and preferably decomposes at 100 to 180 ° C. to generate gas.
Examples of the pyrolytic foaming agent include urea, urea derivatives, dinitrosopentamethylenetetramine, amidoguanidine, trimethylenetriamine, paratoluenesulfone hydrazine, azodicarbonamide, thiourea, ammonium chloride, dicyandiamide, dioxane, hexane, and water Examples include chloral and citric acid. In particular, urea is a suitable blowing agent.
When the content of the pyrolytic foaming agent is small, the foaming degree of the resulting acrylic resin foam may be reduced and the lightness may be impaired. There is a risk that it is difficult to uniformly dissolve the decomposable foaming agent, the thermal decomposable foaming agent tends to remain in the resulting acrylic resin foam, or foam breakage occurs.
Therefore, the pyrolytic foaming agent is preferably contained in the polymerizable solution at a ratio of 0.5 to 30 parts by mass when the total amount of polymerizable monomers is 100 parts by mass. When the mold blowing agent is urea, it is preferable that the polymerizable solution contains 1 to 15 parts by mass when the total amount of the polymerizable monomers is 100 parts by mass.
As other foaming agents other than the pyrolytic foaming agent, a physical foaming agent (alcohol etc.) having a boiling point of 65 ° C. or higher can be used, and a physical foaming agent (alcohol etc.) having a boiling point of 65 ° C. to 180 ° C. is preferred. . Specific examples include alcohols such as isopropanol, cyclopentanol, ethanol, 1-propanol, 2-methyl-2-propanol, and 2-ethyl-1-hexanol. A physical foaming agent is not effective even when used alone, and is effective when used in combination with a pyrolytic foaming agent. As a usage-amount, when making the total amount of a polymerizable monomer into 100 mass parts, it is preferable to make it contain in a polymerizable solution in the ratio which will be 0.6-30 mass parts with the total amount with a thermal decomposition type foaming agent. .

(Polymerization initiator)
As the polymerization initiator, a redox polymerization initiator, a thermal decomposition initiator, a photodecomposition initiator, or the like is used. The higher the decomposition temperature, the more difficult it is to adjust the polymerization rate of the polymerizable solution, but from the viewpoint of easy adjustment of the polymerization rate of the polymerizable solution, it is possible to use a redox polymerization initiator, for example, t-butyl hydroperoxide. preferable.
Specific substances that can be used as redox polymerization initiators other than the t-butyl hydroperoxide include cumene hydroxy peroxide, diisopropylbenzene hydroperoxide, p-menthane hydroperoxide, 1,1,3. , 3-tetramethylbutyl hydroperoxide and the like.
The polymerization initiator is preferably contained in the polymerizable solution at a ratio of 0.1 to 5 parts by mass when the total amount of polymerizable monomers is 100 parts by mass.

(Calcium ion)
In the present embodiment, the polymerizable solution can further contain calcium ions.
As the substance for adding calcium ions, calcium formate, calcium nitrate tetrahydrate and the like can be used, and it is preferable to use at least one of calcium formate and calcium nitrate tetrahydrate.
When acrylic acid or methacrylic acid is used as the polymerizable monomer, in the polymerizable solution, if the concentration of calcium ions is too high, the polymerization of acrylic acid or methacrylic acid is suppressed, and a homogeneous polymerization reaction occurs. It becomes difficult to occur. When at least one of calcium formate and calcium nitrate tetrahydrate is used as the calcium ion-adding substance, a large amount of calcium formate or calcium nitrate tetrahydrate is added to the polymerizable solution so as to increase the concentration of calcium. When it is contained, the undissolved calcium salt (calcium formate or calcium nitrate tetrahydrate) becomes a nucleus during polymerization or polymerization shrinkage, and there is a possibility that bubbles may be generated in the foamable polymer. Further, when foaming polymer containing coarse calcium salt that remains undissolved is foamed, the coarse calcium salt may become bubble nuclei and generate coarse bubbles in the foam. Therefore, the the polymerizable monomer 100 molar parts, preferably the total amount of said calcium formate and the calcium nitrate tetrahydrate is less than 5.0 × 10 ^-2 mol parts, 2.5 × 10 ^- More preferably, it is ² mol parts or less.
On the other hand, in the polymerizable solution, if the concentration of calcium ions is too low, single polymerization of acrylic acid or methacrylic acid, which tends to be a single polymer, is likely to occur, and the bubble diameter in the foam is uniform. The total amount of the calcium formate and the calcium nitrate tetrahydrate is preferably 2.5 × 10 ⁻⁴ mol part or more with respect to 100 mol parts of the polymerizable monomer. It is more preferably 0 × 10 ⁻⁴ mol part or more.
In addition, the calcium salt that remains undissolved in the polymerizable solution becomes bubble nuclei in the foamable polymer and facilitates the formation of uniform bubbles in the foam. Therefore, the calcium salt that remains undissolved remains in the polymerizable solution. It is desirable to produce a foamable polymer by polymerizing the polymerizable monomer.

(Anhydrous sodium sulfate)
Furthermore, in the present embodiment, the polymerizable solution may further contain anhydrous sodium sulfate. In addition, since anhydrous sodium sulfate has been conventionally used for removing water contained in the polymerizable solution, it has been removed by filtration using filter paper before the polymerizable monomer is polymerized. However, in this embodiment, the polymerizable monomer is polymerized while anhydrous sodium sulfate is contained in the polymerizable solution.
In the polymerizable solution, if the concentration of anhydrous sodium sulfate is too high, there may be a problem because the foamable polymer after polymerization contains a large amount of anhydrous sodium sulfate. That is, anhydrous sodium sulfate present in the polymerizable solution becomes a nucleus during polymerization or polymerization shrinkage, and there is a possibility that bubbles may be generated in the foamable polymer. Moreover, when foaming polymer containing anhydrous sodium sulfate excessively is foamed, anhydrous sodium sulfate may become bubble nuclei and generate coarse bubbles. Therefore, the amount of anhydrous sodium sulfate is preferably 3.0 × 10 ⁻² parts by mass or less and more preferably 1.5 × 10 ⁻² parts by mass or less with respect to 100 parts by mass of the polymerizable monomer.
On the other hand, in the polymerizable solution, if the concentration of anhydrous sodium sulfate is too low, the uniformity of the bubble diameter in the foam may be impaired or the bubble diameter may be increased. On the other hand, the amount of anhydrous sodium sulfate is preferably 6.0 × 10 ⁻⁴ parts by mass or more, and more preferably 9.0 × 10 ⁻⁴ parts by mass or more.

(Plasticizer)
In the present embodiment, the polymerizable solution may further contain a plasticizer.
Examples of the plasticizer include phthalic acid ester, adipic acid ester, trimellitic acid ester, polyester, phosphoric acid ester, citric acid ester, epoxidized vegetable oil, sebacic acid ester, azelaic acid ester, maleic acid ester, benzoic acid ester, sulfone. An acid ester or the like is used.
Examples of the phthalic acid ester include dioctyl phthalate, diisononyl phthalate, diisodecyl phthalate, and dibutyl phthalate. Examples of the adipic acid ester include dioctyl adipate, diisononyl adipate, diisobutyl adipate, dibutyl adipate, and the like. Examples of the trimellitic acid ester include trioctyl trimellitic acid. Examples of the phosphate ester include tricresyl phosphate, triamyl phosphate, and tributyl phosphate. Examples of the citric acid ester include acetyl tributyl citrate, triethyl citrate, and triethyl acetyl citrate. Examples of the epoxidized vegetable oil include epoxidized soybean oil and epoxidized linseed oil. Examples of the sulfonic acid esters include alkyl sulfonic acid phenyl esters, and examples of commercially available sulfonic acid esters include Mesamol from LANXESS.
As the plasticizer, dioctyl phthalate, diisobutyl adipate, tributyl acetylcitrate, sulfonate, and the like are preferably used.
If the amount of the plasticizer is small, the foamability of the foamable polymer may be insufficient. If the amount is large, the rigidity of the obtained acrylic resin foam may be reduced, or the bubbles of the acrylic resin foam may be coarsened. Or the acrylic resin foam may shrink at the time of foaming. When the total amount of the polymerizable monomer is 100 parts by mass, it is contained in the polymerizable solution in a ratio of 0.1 to 20 parts by mass. It is preferable that 0.3-10 mass parts is more preferable, and 0.5-5 mass parts is especially preferable.

(Reducing agent)
Furthermore, in the present embodiment, the polymerizable solution can further contain a reducing agent.
As the reducing agent, a compound capable of reducing (donating electrons) other compounds such as a nitrogen-containing compound such as N, N-dimethylaniline can be used.
Specific examples of nitrogen-containing compounds other than N, N-dimethylaniline that can be used as a reducing agent include amine compounds such as triethylamine.
The reducing agent is preferably contained in the polymerizable solution in a weight ratio of 0.1 to 5 times the content of the polymerization initiator.

(Metal ions, chloride ions)
In the present embodiment, the polymerizable solution includes one or more metal ions selected from the group consisting of Cu ⁺ , Cu ²⁺ , Fe ³⁺ , Ag ⁺ , Pt ²⁺ , and Au ^3+. Further, chloride ions can be further contained.
Each of the metal ions has a positive oxidation-reduction potential.
Further, the metal ion functions as an electron-donating substance, that is, an oxidizing agent, or an electron-donating substance, that is, a reducing agent, in the polymerizable solution, and accelerates the polymerization reaction of the polymerizable monomer. It contributes to.
On the other hand, the chloride ion contributes to the promotion of the polymerization reaction of the polymerizable monomer by binding or desorption from the metal ion.

The above metal ions and chloride ions may be contained in the polymerizable solution at the same time in the form of copper chloride, ferric chloride, silver chloride, gold chloride, and may be polymerized by separate substances. You may make it contain in a solution.
In addition to the above chlorides, for example, the above-described metal ions may be contained in the polymerizable solution by a substance such as copper bromide, copper iodide, copper stearate, copper naphthenate, or silver bromide. it can.
In addition, about copper, silver, and gold | metal | money, the ion can be contained in a polymeric solution not by the above salts but by the metal itself or an alloy.
For example, copper, copper alloy (constantan: copper / nickel alloy, brass: copper / zinc alloy), silver, gold fine particles, wires, mesh, etc. are mixed in the polymerizable solution to polymerize these ions. Can be contained.

  Examples of specific substances for containing chloride ions in the polymerizable solution include 1,3-dimethylimidazolium chloride, 1-butyl-3-methylimidazolium in addition to sodium chloride and hydrochloric acid, for example. Chloride, 1-butyl-2,3-dimethylimidazolium chloride, 1-ethyl-3-methylimidazolium chloride, 1-methyl-3-n-octylimidazolium chloride, 1-methyl-1-hydroxyethyl-2- Tallow alkyl-imidazolium chloride and other imidazolium salt type surfactants, hexatrimethylammonium chloride, dodecylyltrimethylammonium chloride, stearyltrimethylammonium chloride, coconut alkyltrimethylammonium chloride, beef tallow alkyltrimethy Ammonium chloride, behenyl trimethyl ammonium chloride, poly diallyl dimethyl ammonium chloride, dialkyl dimethyl ammonium chloride, cetyl trimethyl ammonium chloride, and the like quaternary ammonium salt type surfactants such as lauryl trimethyl ammonium chloride.

In addition, as a specific substance for containing the chloride ion in the polymerizable solution, any one of sodium chloride, hydrochloric acid, hexatrimethylammonium chloride, dialkyldimethylammonium chloride, cetyltrimethylammonium chloride, and lauryltrimethylammonium chloride. In particular, it is preferable to employ cetyltrimethylammonium chloride.
In the case where these chloride ion-containing substances are contained in the polymerizable solution, usually, in a ratio of 0.005 to 5 parts by mass when the total amount of the polymerizable monomers in the polymerizable solution is 100 parts by mass. It can be included.

In addition, specific materials for containing the metal ions in the polymerizable solution include silver chloride, copper chloride, copper stearate, copper naphthenate, ferric chloride, or copper (copper particles and copper wire). Is preferred.
When these are contained in the polymerizable solution, the ratio is usually 1 × 10 ⁻¹⁰ to 1 × 10 ⁻² parts by mass when the total amount of the polymerizable monomers in the polymerizable solution is 100 parts by mass. It can be included.

(Acrylic resin foam)
In the present embodiment, the polymerizable solution may further contain an acrylic resin foam obtained by foaming a foamable polymer of a polymerizable monomer that is the same as or different from the polymerizable monomer.
The acrylic resin foam contributes to the acceleration of the polymerization reaction of the polymerizable monomer in the polymerizable solution.
The acrylic resin foam is preferably 0.1 to 20 parts by mass, more preferably 1 to 15 parts by mass, and even more when the total amount of polymerizable monomers in the polymerizable solution is 100 parts by mass. Preferably it is contained in the polymerizable solution at a ratio of 5 to 10 parts by mass.
In the polymerizable solution, when the acrylic resin foam is 20 parts by mass or less with respect to 100 parts by mass of the total amount of polymerizable monomers, the acrylic resin foam is uniformly dissolved in the polymerizable monomer. It has the advantage of being easy. In addition, the polymerizable solution is such that the acrylic resin foam is 0.1 parts by mass or more with respect to 100 parts by mass of the total amount of polymerizable monomers, so that the polymerizable monomer in the polymerizable solution is polymerized. Has the advantage of being promoted.

(Foaming polymer production process)
In the foaming polymer preparation step, the polymerizable monomer in the polymerizable solution is polymerized by heating the polymerizable solution at a temperature equal to or higher than the temperature at which the polymerizable monomer is polymerized and lower than the temperature at which the foaming agent is decomposed. This is a step of producing a foamable polymer.
The temperature for heating the polymerizable solution is preferably a temperature lower than the decomposition temperature of the foaming agent to be used (the temperature of the foaming agent having the lowest decomposition temperature when plural kinds of foaming agents are used). A temperature that is at least 10 ° C. lower than the temperature is preferred.

(Foam production process)
The foam preparation step is a step of heating the foamable polymer at a temperature equal to or higher than the temperature at which the foaming agent decomposes to decompose the foaming agent to form an acrylic resin foam.
The temperature at which the foamable polymer is heated is preferably a temperature equal to or higher than the decomposition temperature of the foaming agent used (the temperature of the foaming agent having the highest decomposition temperature when a plurality of types of foaming agents are used). A temperature higher by 10 ° C. or more than the decomposition temperature is preferable. About this heating temperature, it is preferable to set it as 200 degrees C or less. By making this heating temperature 200 or less, it can suppress that an acrylic resin foam shrink | contracts with a heat | fever.

  According to the method for producing an acrylic resin foam of the present embodiment, it contains a polymerizable monomer containing an acrylic monomer, a foaming agent such as urea, and a polymerization initiator, and contains calcium and sodium. A foamable polymer obtained by preparing a polymerizable solution having a calcium concentration of 2 to 150 μg / g and a sodium concentration of 2 to 50 μg / g, polymerizing the polymerizable monomer, and then polymerizing the polymerizable monomer. By foaming, an acrylic resin foam that is excellent in heat resistance and lightness and tends to be small in variation in cell diameter can be obtained.

Next, the acrylic resin foam according to this embodiment will be described.
The acrylic resin foam according to the present embodiment contains calcium and sodium.

Moreover, it is important that the calcium concentration of the acrylic resin foam according to the present embodiment is 2 to 150 μg / g, and preferably 45 to 85 μg / g. Moreover, it is important that the sodium concentration of the acrylic resin foam according to the present embodiment is 2 to 50 μg / g, and preferably 20 to 45 μg / g.
Furthermore, the acrylic resin foam according to this embodiment has a calcium concentration of 2 to 150 μg / g and a sodium concentration of 2 to 50 μg / g, so that the variation in the bubble diameter tends to be small. Have advantages.
The concentration of calcium and sodium in the acrylic resin foam is determined by ashing the acrylic resin foam, mixing the ash and concentrated hydrochloric acid, and diluting with distilled water for ICP emission spectroscopic analysis. Can be obtained.

Moreover, it is preferable that the variation coefficient of the bubble diameter of the acrylic resin foam according to the present embodiment is 45% or less.
The variation coefficient of the bubble diameter can be measured by the following method.
First, with respect to the acrylic resin foam, a 10 mm × 10 mm × 10 mm square is cut out from the foam surface except 1/10 of the foam thickness. If the acrylic resin foam is too small to cut out a 10 mm × 10 mm × 10 mm square, cut out as much as possible.
Then, using a scanning electron microscope (for example, “S-3000N” manufactured by Hitachi, Ltd.), each of the three cut surfaces that are not parallel to each other is magnified 18 to 100 times and photographed. Each of the cut surface images is printed on A4 paper. At this time, the magnification of the electron microscope is adjusted so that the number of bubble diameters in the printed photograph is 300 or more, and printing is performed on A4 paper. If the number of bubble diameters does not exceed 300 per cut surface, the cut surface is imaged multiple times.
Next, all the independent bubbles that can be confirmed in the visual field are selected, the diameter of the selected bubbles (bubble diameter) is measured, and the arithmetic average value (average bubble diameter for each cut surface) is obtained for each cut surface.
In addition, about each bubble diameter, the center of the cross-sectional shape of a bubble is calculated | required and let the length of the longest part in the linear distance which passes the center be a bubble diameter.
And about the average cell diameter (overall average cell diameter) of an acrylic resin foam, a geometric average value is calculated | required from the average cell diameter for every cut surface, and this geometric average value is obtained for the average cell diameter ( Overall average bubble diameter).
Then, the standard deviation is calculated from all the bubble diameters measured by the following formula, and the variation coefficient of the bubble diameter is obtained.

変動係数（％） ＝ 標準偏差／全体の平均気泡径×１００

Coefficient of variation (%) = standard deviation / total average bubble diameter x 100

Furthermore, the open cell ratio of the acrylic resin foam according to the present embodiment is preferably 25% or less, and more preferably 8 to 20%.
When the acrylic resin foam according to the present embodiment has an open cell ratio of 25% or less, when the FRP sheet or the like is adhered to the surface of the acrylic resin foam with an adhesive, the amount of the adhesive is reduced. It has the advantage that it can be suppressed, and also has the advantage that it can suppress deformation when pressurized.
The open cell ratio of the acrylic resin foam can be measured by the 1-1 / 2-1 atmospheric pressure method in accordance with ASTM D-2856-87.

In addition, the acrylic resin foam according to the present embodiment preferably has an apparent density of 0.15 g / cm ³ or less, more preferably 0.12 g / cm ³ or less, from the viewpoint of lightness. On the other hand, if the apparent density is too small, the mechanical strength is lowered, so that it is preferably 0.03 g / cm ³ or more, and more preferably 0.04 g / cm ³ or more.
The apparent density can be measured according to the method described in JIS K 7222: 2005 “Foamed Plastics and Rubber—How to Obtain the Apparent Density”.

  In addition, although the manufacturing method of the acrylic resin foam which concerns on this embodiment, and the acrylic resin foam had the said advantage by the said structure, the manufacturing method of the acrylic resin foam of this invention In addition, the acrylic resin foam is not limited to the above configuration, and can be appropriately changed in design.

  Next, the present invention will be described more specifically with reference to examples and comparative examples.

(Evaluation)
The example which performed various evaluation about the acrylic resin foam is shown.
First, an evaluation method for a foamable polymer and an acrylic resin foam will be described.

(Density of foamable polymer)
About the test piece of 10 cm < ³ > or more cut | disconnected so that a crack might not arise in an expandable polymer, the mass was measured and the density was computed by following Formula.
Density (g / cm ³ ) = Test piece mass (g) / Test piece volume (cm ³ )

(Concentration of Ca (calcium) and concentration of Na (sodium) in acrylic resin foam)
The calcium concentration (Ca concentration) and the sodium concentration (Na concentration) of the acrylic resin foam were measured by the methods described above. Specifically, it measured as follows.
First, as a pretreatment, the acrylic resin foam is finely cut, about 0.5 to 2.0 g of the cut sample is placed in a crucible and precisely weighed, and the cut sample in the crucible is ashed under the following ashing conditions. The incinerated product and 2 mL of concentrated hydrochloric acid were mixed to obtain a mixed solution. Then, this mixed solution was filtered with a filter paper (Toyo Filter Paper, ADVANTEC No. 7) to remove insoluble matters. Next, the mixed solution from which insolubles had been removed was diluted with distilled water and the volume was adjusted to 50 mL to prepare a test solution for ICP measurement.
Next, the measurement solution was subjected to ICP emission spectroscopic analysis under the following ICP measurement conditions, and the Ca concentration and the Na concentration in the measurement solution were calculated from the calibration curve. When either the calcium concentration or sodium concentration in the test solution exceeded the upper limit of the calibration curve, the test solution was further diluted with distilled water so that it was within the range of the calibration curve. .
And the density | concentration of the calcium in an acrylic resin foam and the density | concentration of sodium were computed from the following formula.
Calcium concentration in acrylic resin foam (μg / g) = Calcium concentration in measurement solution (μg / mL) × 50 (mL) ÷ Sample mass (g)
Sodium concentration in acrylic resin foam (μg / g) = Sodium concentration in measurement solution (μg / mL) × 50 (mL) ÷ Sample mass (g)
<Ashing conditions>
Measuring device: Electric furnace Muffle furnace STR-15K (manufactured by Isuzu)
Ashing conditions: 450 ° C. × 3 hr (sample amount = about 0.5 to 2.0 g)
<ICP measurement conditions>
Measuring device: Multi-type ICP emission spectroscopic analyzer ICPE-9000 manufactured by Shimadzu Corporation
Measurement elements: Ca (317.933 nm), Na (5899.592 nm)
Observation direction = axial direction, high frequency output = 1.20 kW, carrier flow rate = 0.7 L / min, plasma flow rate = 10.0 L / min, auxiliary flow rate = 0.6 L / min, exposure time = 30 seconds, standard for calibration curve Liquid: US SPEX XSTC-13 (general-purpose mixed standard solution) 31 elements mixed (base 5% by mass HNO ₃ )-about 10 mg / L each
Calibration curve preparation method: The above standard curve standard solution was diluted with distilled water in stages to prepare standard solutions of 0 ppm (blank), 0.2 ppm, 1.0 ppm, 2.5 ppm and 5 ppm. The standard solution of each concentration was measured under the above conditions, and the peak intensity of the wavelength of each element was obtained. Concentration and peak intensity were plotted to obtain an approximate curve (straight line or quadratic curve) by the least square method, and this was used as a calibration curve for quantification.

(Apparent density of acrylic resin foam)
The apparent density of the acrylic resin foam was measured by the following method. Specifically, a test piece having a length of 25 mm, a width of 25 mm, and a thickness of 25 mm is cut from a sample that has passed 72 hours or more after molding of the foam so as not to change the structure of the original bubbles of the material, K7100: Symbol 23/50 of 1999, after conditioning for 16 hours in a second grade environment, the dimensions and mass of the test piece were measured and calculated according to the following equation. Note that a “DIGIMATIC” CD-15 type manufactured by Mitutoyo Corporation was used for measuring the dimensions of the test piece.
Apparent density (g / cm ³ ) = 10 ³ × test piece mass (g) / test piece volume (mm ³ )

(Average cell diameter of acrylic resin foam and coefficient of variation of cell diameter)
The average cell diameter of the acrylic resin foam and the coefficient of variation of the cell diameter were determined by the method described above.
For measurement of the bubble diameter, “DIGIMATIC” CD-15 type manufactured by Mitutoyo Corporation was used, and was calculated from the following equation.
Bubble diameter (mm) = Actual measured value of maximum linear distance of bubbles (mm) / Magnification of photograph Here, the magnification of photograph is measured to 1 / 100mm with "Digimatic Caliper" made by Mitutoyo Corporation with the scale bar on the photograph. And obtained from the following equation.
Magnification of photo = Scale bar measured value (mm) / Scale bar display value (mm)

(Open cell ratio of acrylic resin foam)
The open cell ratio of the acrylic resin foam was measured by the following method. That is, the acrylic resin foam was cut out so as not to have a molding surface skin on all six surfaces of the molded body, and the cut surface was finished with a pan slicer to produce three 25 mm × 25 mm × 25 mm cubic test pieces. . Each test piece was conditioned for 16 hours in a JIS K7100-1999 symbol 23/50, second grade environment, and then measured in a JIS K7100-1999 symbol 23/50, second grade environment. The measurement of the open cell ratio of each test piece was performed as follows. First, the outer dimension of the measurement sample was measured to 1/100 mm using a “DIGIMATIC” CD-15 type manufactured by Mitutoyo Corporation to determine the apparent volume (cm ³ ). Next, the volume (cm < ³ >) of the measurement sample was calculated | required by the 1-1 / 2-1 atmospheric pressure method using the air comparison type hydrometer 1000 type | mold (Tokyo Science Co., Ltd. product). The open cell ratio (%) was calculated from the value obtained above and the following formula, and the arithmetic average value of three tests was obtained. The air comparison hydrometer was corrected with a standard sphere (large 28.9 cc, small 8.5 cc).
Open cell ratio (%) = 100 × (apparent volume−volume measured with an air-based hydrometer) / apparent volume

Example 1
5 parts by mass of urea as a foaming agent is mixed with 100 parts by mass of a polymerizable monomer composed of 60% by mass of methyl methacrylate, 20% by mass of methacrylic acid, and 20% by mass of styrene, and the monomer solution is uniformly dissolved. Was made.
Furthermore, 0.48 parts by mass of t-butyl hydroperoxide (“Perbutyl H-69” manufactured by NOF Corporation) as a polymerization initiator and N, N-dimethyl as a reducing agent with respect to 100 parts by mass of the polymerizable monomer. 0.48 parts by mass of aniline, 0.06 parts by mass of hexatrimethylammonium chloride as a substance for adding chloride ions (“Nissan Cation PB-300” manufactured by NOF Corporation), 0.0007 of calcium formate as a substance for adding calcium ions Mass parts (5.3 × 10 ⁻⁴ mol parts relative to 100 mol parts of polymerizable monomer) and 9.3 × 10 ⁻⁴ mass parts of anhydrous sodium sulfate are added to the monomer solution, and these are stirred to obtain a polymerizable solution. Was made.
1000 g of the polymerizable solution was placed in a glass cuboid mold having an internal method of 25 mm × 120 mm × 300 mm. And the foaming polymer (density: 1.15 g / cm < ³ >) was obtained by putting the polymeric solution into a thermostat with the mold and heating at 50 degreeC for 10 hours. At this time, it was confirmed that the foamable polymer was cured.
Thereafter, the obtained foamable polymer was cut into 25 mm × 100 mm × 150 mm, put into a mold having an internal method of 70 mm × 200 mm × 300 mm, and the foamable polymer was put together with the mold into a hot air circulating furnace at 170 ° C. Acrylic resin foam (apparent density: 0.115 g / cm ³ ) was obtained by heating for 30 minutes.

(Example 2)
An acrylic resin foam was obtained in the same manner as in Example 1 except that the amount of anhydrous sodium sulfate was changed to 1.5 × 10 ⁻² parts by mass with respect to 100 parts by mass of the polymerizable monomer.

(Example 3)
The amount of calcium formate with respect to 100 parts by mass of the polymerizable monomer is 1.7 × 10 ⁻² parts by mass (1.3 × 10 ⁻² mol with respect to 100 parts by mol of the polymerizable monomer), and the amount of anhydrous sodium sulfate is An acrylic resin foam was obtained in the same manner as in Example 1 except that the content was 8.0 × 10 ⁻³ parts by mass.

Example 4
The amount of calcium formate with respect to 100 parts by mass of the polymerizable monomer is 4.0 × 10 ⁻² parts by mass (3.0 × 10 ⁻² mol with respect to 100 parts by mol of the polymerizable monomer), and the amount of anhydrous sodium sulfate is An acrylic resin foam was obtained in the same manner as in Example 1 except that the amount was 9.3 × 10 ⁻⁴ parts by mass.

(Example 5)
The amount of calcium formate with respect to 100 parts by mass of the polymerizable monomer is 4.0 × 10 ⁻² parts by mass (3.0 × 10 ⁻² mol with respect to 100 parts by mol of the polymerizable monomer), and the amount of anhydrous sodium sulfate is An acrylic resin foam was obtained in the same manner as in Example 1 except that the amount was 1.5 × 10 ⁻² parts by mass.

(Example 6)
Calcium nitrate tetrahydrate is used in place of calcium formate, and calcium nitrate tetrahydrate is 3.1 × 10 ⁻² parts by weight (100 parts by weight of polymerizable monomer) with respect to 100 parts by weight of polymerizable monomer. An acrylic resin foam was obtained in the same manner as in Example 3 except that the amount was 1.3 × 10 ⁻² mol part).

(Comparative Example 1)
An insoluble material is obtained by filtering the polymerizable solution obtained in the same manner as in Example 3 with a filter paper (two filter papers defined in “Filter paper (for chemical analysis)” of JIS P3801: 1995) as a liquid to be treated. Acrylic resin foam was obtained in the same manner as in Example 3 except that the obtained filtrate was placed in a glass cuboid mold as a polymerizable solution.

(Comparative Example 2)
The amount of calcium formate with respect to 100 parts by mass of the polymerizable monomer is 1.5 × 10 ⁻³ parts by mass (1.1 × 10 ⁻³ mol with respect to 100 parts by mol of the polymerizable monomer), and the amount of anhydrous sodium sulfate is An acrylic resin foam was obtained in the same manner as in Example 1 except that the content was 3.1 × 10 ⁻⁴ parts by mass.

(Comparative Example 3)
The amount of calcium formate with respect to 100 parts by mass of the polymerizable monomer is 6.8 × 10 ⁻² parts by mass (5.1 × 10 ⁻² mol with respect to 100 parts by mol of the polymerizable monomer), and the amount of anhydrous sodium sulfate is An acrylic resin foam was obtained in the same manner as in Example 1 except that the content was 8.0 × 10 ⁻³ parts by mass.

(Comparative Example 4)
The amount of calcium formate with respect to 100 parts by mass of the polymerizable monomer is 1.7 × 10 ⁻² parts by mass (1.3 × 10 ⁻² mol with respect to 100 parts by mol of the polymerizable monomer), and the amount of anhydrous sodium sulfate is An acrylic resin foam was obtained in the same manner as in Example 1 except that the content was 3.1 × 10 ⁻⁴ parts by mass.

(Comparative Example 5)
The amount of calcium formate with respect to 100 parts by mass of the polymerizable monomer is 1.7 × 10 ⁻² parts by mass (1.3 × 10 ⁻² mol with respect to 100 parts by mol of the polymerizable monomer), and the amount of anhydrous sodium sulfate is An acrylic resin foam was obtained in the same manner as in Example 1 except that the amount was 3.7 × 10 ⁻² parts by mass.

  The test results are shown in Table 1.

As shown in Table 1, the acrylic resin foams of Examples 1 to 6 within the scope of the present invention have Comparative Examples 1, 2, and 4 in which the concentration of sodium is 1 μg / g or less, and the concentration of calcium is 200 μg. The variation coefficient of the cell diameter was small compared to the acrylic resin foam of Comparative Example 3 having a / g concentration and Comparative Example 5 having a sodium concentration of 120 μg / g.
The acrylic resin foam of Comparative Example 1 was a mixture of fine bubbles and coarse bubbles. Thereby, the acrylic resin foam of Comparative Example 1 had a larger average cell diameter and a variation coefficient of the cell diameter than Example 3.
Therefore, according to this invention, it turns out that the acrylic resin foam which becomes easy to become a thing with the variation in a bubble diameter small compared with the past can be provided.

Claims (11)

Contains calcium and sodium,
The concentration of the calcium is 2~150μg / g, the concentration of the sodium Ri 2~50μg / g der,
A polymerizable solution containing a polymerizable monomer containing an acrylic monomer, a foaming agent containing a thermally decomposable foaming agent, and a polymerization initiator is prepared, and the polymerizable monomer is polymerized, and then obtained by the polymerization. Obtained by foaming a foamable polymer,
The polymerizable monomer contains 50 to 70% by weight of methyl methacrylate, 14 to 30% by weight of (meth) acrylic acid, and 10 to 20% by weight of styrene.
The acrylic resin foam in which the polymerizable solution does not substantially contain water . Contains calcium and sodium,
The concentration of the calcium is 2~150μg / g, the concentration of the sodium Ri 2~50μg / g der,
A polymerizable solution containing a polymerizable monomer containing an acrylic monomer, a foaming agent containing a thermally decomposable foaming agent, and a polymerization initiator is prepared, and the polymerizable monomer is polymerized, and then obtained by the polymerization. Obtained by foaming a foamable polymer,
The polymerizable monomer contains 50 to 70% by weight of methyl methacrylate, 14 to 30% by weight of (meth) acrylic acid, and 10 to 20% by weight of styrene.
The acrylic resin foam in which the polymerizable solution contains anhydrous sodium sulfate . The acrylic resin foam according to claim 1 or 2 , wherein the polymerizable solution further contains NN dimethylaniline. The acrylic resin foam according to any one of claims 1 to 3 , wherein a coefficient of variation of a bubble diameter is 45% or less. The acrylic resin foam according to any one of claims 1 to 4 , wherein the open cell ratio is 25% or less. A polymerizable solution containing a polymerizable monomer containing an acrylic monomer, a foaming agent containing a thermally decomposable foaming agent, and a polymerization initiator is prepared, and the polymerizable monomer is polymerized, and then obtained by the polymerization. A step of producing an acrylic resin foam by foaming the foamable polymer,
Containing the calcium and sodium, the concentration of the calcium is 2 to 150 μg / g, and the concentration of the sodium is 2 to 50 μg / g, to produce the acrylic resin foam ,
The polymerizable monomer contains 50 to 70% by weight of methyl methacrylate, 14 to 30% by weight of (meth) acrylic acid, and 10 to 20% by weight of styrene.
The manufacturing method of the acrylic resin foam whose said polymeric solution does not contain water substantially . A polymerizable solution containing a polymerizable monomer containing an acrylic monomer, a foaming agent containing a thermally decomposable foaming agent, and a polymerization initiator is prepared, and the polymerizable monomer is polymerized, and then obtained by the polymerization. A step of producing an acrylic resin foam by foaming the foamable polymer,
Containing the calcium and sodium, the concentration of the calcium is 2 to 150 μg / g, and the concentration of the sodium is 2 to 50 μg / g, to produce the acrylic resin foam ,
The polymerizable monomer contains 50 to 70% by weight of methyl methacrylate, 14 to 30% by weight of (meth) acrylic acid, and 10 to 20% by weight of styrene.
The method for producing an acrylic resin foam , wherein the polymerizable solution contains anhydrous sodium sulfate . The method for producing an acrylic resin foam according to claim 6 or 7 , wherein the polymerizable solution further contains calcium ions and anhydrous sodium sulfate.   The method for producing an acrylic resin foam according to claim 8, wherein at least one of calcium formate and calcium nitrate tetrahydrate is used as the substance for adding calcium ions contained in the polymerizable solution. In the polymerizable solution, the total amount of the calcium formate and the calcium nitrate tetrahydrate is 2.5 × 10 ^{−4 to} 5.0 × 10 ⁻² mol with respect to 100 mol of the polymerizable monomer. A method for producing an acrylic resin foam according to claim 9. The said polymerizable solution WHEREIN: The said anhydrous sodium sulfate is 6.0 * 10 ^{< -4} > -3.0 * 10 ^<-2 > mass part with respect to 100 mass parts of said polymerizable monomers, The any one of Claims 8-10. The manufacturing method of the acrylic resin foam as described in any one of.