JP2014076598A - Plastic eraser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plastic eraser excellent in anti-transition properties of plasticizer, less stick on a surface of the eraser, and yet excellent in erasing properties.SOLUTION: A plastic eraser includes base material resin, plasticizer, and filler. The plasticizer includes liquid polymer being liquid at ordinary temperature and having the SP value of 8.75 or more, and one kind of ester plasticizer other than the liquid polymer. The rate of the liquid polymer in the entire plasticizer is 0.5 mass% or more and 20 mass% or less.

Description

  The present invention relates to a plastic eraser, and more particularly to a plastic eraser with a high erase rate, excellent plasticizer migration resistance (ie, a small amount of plasticizer migration), and less stickiness.

  Erasers (commonly known as erasers) are widely used as indispensable for erasing writing lines because of their excellent erasability. The eraser is generally blended with a plasticizer in the base resin, and if necessary, eraser materials such as stabilizers, coloring agents, and fragrances are added as appropriate and mixed and stirred, followed by press molding, injection molding, It is manufactured by heating and molding by a molding method such as extrusion molding.

  Plasticizers are used to impart flexibility, durability, cold resistance, electrical properties, etc. to the base resin, but in plastic erasing, from the aspect of erasing, graphite, which is the erasure target substance For example, plasticizers having an affinity for the like are frequently used. Conventionally, phthalic acid-based plasticizers have been widely used, and di-2-ethylhexyl phthalate, di-n-butyl phthalate and the like have been used, but in recent years, aliphatic and aromatic ester plasticizers, Non-phthalic acid plasticizers, such as liquid polymers, that have a low impact on the human body and the environment have been developed (see, for example, Patent Documents 1 and 2).

  However, since the plastic eraser contains a large amount of plasticizer, when it is brought into close contact with a resin molded product, bleeding of the plasticizer that dissolves and erodes them occurs. Although it is conceivable to raise the molding temperature in order to suppress the migration, there is a limit to the molding temperature in view of the thermal stability of the base resin and other additives, and the economy is also deteriorated.

  On the other hand, depending on the plasticizer, even if the migration resistance is good, the plasticizer may ooze out on the erased surface and cause stickiness. If the surface is sticky, the erasure residue sticks to the paper surface and erases the paper surface when erasing.

  The stickiness of the plastic eraser surface can be eliminated by reducing the blending amount of the plasticizer. However, if the blending amount of the plasticizer is reduced, the original eraseability of the eraser will be lowered.

  As described above, erasing power equivalent to that of conventional products, excellent transition resistance, and erasing without stickiness on the surface are desired, but this transition resistance and surface stickiness have an equal relationship. Therefore, it is more difficult than expected to satisfy these characteristics at the same time.

JP 2005-138359 A JP-A-5-147392

  An object of the present invention is to provide a plastic eraser that is excellent in migration resistance of a plasticizer, has no stickiness on the erased surface, and has excellent eraseability.

  In order to solve the above-mentioned problems, the present inventor has intensively studied and the ester plasticizer has a high erasure rate and excellent migration resistance. However, the ester plasticizer is used as a main component of the plasticizer. We paid attention to the tendency of stickiness to occur. By using a small amount of a liquid polymer having a specified SP value while using this ester plasticizer as a main component of the plasticizer, the problem is solved without reducing the high erasability inherently possessed by the ester plasticizer. As a result, the inventors have found that the problems of erasability, migration resistance, and stickiness, which have been described above, can be solved at once.

  That is, the present invention relates to a plastic eraser containing a base resin, a plasticizer, and a filler, and has a SP value of 8.75 or more as a plasticizer and a liquid polymer that is liquid at room temperature, and at least one other than the liquid polymer. There is provided a plastic eraser characterized in that the proportion of the liquid polymer in the total plasticizer is 0.5 mass% or more and less than 20 mass%.

  In the plastic eraser of the present invention, the liquid polymer is preferably at least one selected from a liquid acrylic polymer and a liquid polyester. The weight average molecular weight (Mw) of the liquid acrylic polymer is preferably 1,800 to 10,000, and the weight average molecular weight (Mw) of the liquid polyester is preferably 800 to 4,000.

  According to the present invention, there is provided a plastic eraser having a high erase rate, excellent migration resistance, no stickiness on the surface, and excellent economic efficiency. In addition, conventionally, there has been a tendency that when the erasability is improved, the strength (folding resistance) is decreased, or when the strength is improved, the erasability is decreased. There is no shortage problem, and it can be used as an eraser.

  The base resin used for the plastic eraser of the present invention includes vinyl chloride resin, vinyl acetate resin, ethylene-vinyl acetate copolymer resin, acrylate ester resin, polyisoprene (natural rubber), styrene, butadiene Type, isoprene-based, ethylene-propylene-based, nitrile-based, chloroprene-based, urethane-based, acrylic-based, polyester-based, and olefin-based elastomers. These base resins are used alone or in combination of two or more as required. Among these resins, a vinyl chloride resin that is easily mixed with a plasticizer and excellent in erasing power is particularly preferable.

  As the vinyl chloride resin, all conventionally used vinyl chloride resins can be used. For example, in addition to polyvinyl chloride having a polymerization degree of about 400 to 3,000, a vinyl chloride-vinyl acetate copolymer, chloride Examples include vinylidene, vinyl chloride-methyl acrylate copolymer, vinyl chloride-methyl methacrylate copolymer, and vinyl chloride-octyl acrylate copolymer. These may be used alone or in combination of two or more as required. As the vinyl chloride resin, a paste resin is preferable because it can be easily mixed and processed with a plasticizer.

  The liquid polymer used in the present invention needs to have an SP value of 8.75 or more. When the SP value is less than 8.75, the compatibility with the ester plasticizer is inferior, and the plastic erased surface is sticky. Therefore, it is difficult to obtain desired erasing. The SP value is more preferably 8.91 or more and 10.00 or less, and further preferably 8.91 or more and 9.50 or less. When the SP value exceeds 10.00, the compatibility with the ester plasticizer is inferior as in the case where the SP value is low, and the liquid polymer tends to be sticky.

  The viscosity of the liquid polymer is preferably 200 to 20,000 (mPa · s / 25 ° C.), more preferably 400 to 10,000 (mPa · s / 25 ° C.). When the viscosity is less than 200 (mPa · s / 25 ° C.), the storage stability after the eraser material is dispersed is deteriorated. On the other hand, when the viscosity exceeds 20,000 (mPa · s / 25 ° C.), the handling property is deteriorated. And it causes stickiness.

  The liquid polymer used in the present invention is liquid at room temperature, and preferably has a glass transition point (Tg) of 10 ° C. or lower. When the glass transition point (Tg) is high, not only is the handling property inferior, but the miscibility with the base resin or the ester plasticizer is deteriorated, and it is difficult to improve the migration resistance of the ester plasticizer. Because it becomes. The glass transition point (Tg) is measured by the DSC method.

  As the liquid polymer, at least one selected from a liquid acrylic polymer and a liquid polyester is preferably used. This is because these liquid polymers are less sticky per se, and have good compatibility with ester plasticizers and base resins (particularly vinyl chloride resins), and are excellent in moldability and handling properties. These liquid polymers can be used alone or in combination as required.

  In liquid acrylic polymers and liquid polyesters, the lower the glass transition point (Tg), the easier the handling and molding of the eraser material during kneading and stirring. In the case of a liquid acrylic polymer, the glass transition point (Tg) is more preferably −30 ° C. or less, and particularly preferably −50 ° C. or less. In the case of liquid polyester, the glass transition point (Tg) is more preferably 0 ° C. or lower.

  Specific examples of the liquid acrylic polymer include ARUFON UP-1000, UP-1010, UP-1020, UP-1021, UP-1061, UP-1080, UP-1190 (all are trade names, Toagosei Co., Ltd.). Etc.). These may be used alone or in combination of two or more as required.

  As the liquid polyester, an adipic acid-based polyester plasticizer obtained by condensing adipic acid, at least one kind of polyhydric alcohol and at least one kind selected from monohydric alcohol or monovalent carboxylic acid is preferably used. It is done.

  Examples of the polyhydric alcohol include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-n-butyl-2-ethyl- 1,3-propanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl1,3-pentanediol, 2,4-ethyl-1,3-hexane Diol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, etc. Aliphatic glycols and diethylene prime 2-18 include polyalkylene glycols such as dipropylene glycol. These polyhydric alcohols are used singly or as a mixture of two or more.

  Examples of monohydric alcohols include monohydric alcohols of carbon 9-18 such as nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, hexadecanol, octadecanol, etc., one or more kinds A mixture is used.

  As monovalent carboxylic acid, C9-C18 carboxylic acids, such as nonanoic acid, capric acid, undecyl acid, lauric acid, are mentioned, for example, 1 type, or 2 or more types of mixtures are used.

  The adipic acid-based polyester may be obtained by using a trivalent or higher polyhydric alcohol such as glycerin or pentaerythritol and a polybasic acid as a modifier, if necessary.

  Specific examples of adipic acid polyesters include Adekasizer PN-150, PN-170, PN-220, PN-230, PN-250, PN-260, PN-280, PN-310, PN-350, PN-400, PN-446, PN-650, PN-850, PN-1010, PN-1020, PN-1030, PN-1430, PN-3030, PN-7160, PN-7230, PN-7310, PN- 7550, PN-7650, PN-9302, P-200, P-300, P-5040 (all are trade names, ADEKA Corporation), Polycizer W-230-H, W-305-ELS, W-320 , W-360-ELS, W-365, W-1020-EL, W-1410-EL, W-1641-S, W-2050, W-20 0, W-2070, W-2145, W-2300-EL, W-2310, W-2340-S, W-2350, W-2370, W-2388, W-2610, W-2630, W-2640- S, W-2650-S, W-4010, P-103 (all are trade names, DIC Corporation) and the like. These may be used alone or in combination of two or more as required.

  As the ester plasticizer other than the liquid polymer in the present invention, a known plasticizer can be used, but it has excellent miscibility with a base resin (especially vinyl chloride resin) and has a high erasing rate. Plasticizers that can be obtained are preferred. The ester plasticizer preferably has a weight average molecular weight (Mw) in the range of 300 to 900. If the molecular weight is less than 300, the migration resistance may be remarkably reduced. If the molecular weight exceeds 900, the compatibility with the base resin is deteriorated, which may cause stickiness. Because. A more preferred weight average molecular weight (Mw) is in the range of 300 to 600.

Examples of ester plasticizers other than liquid polymers include:
Di-2-ethylhexyl phthalate (DOP), di-n-octyl phthalate (n-DOP), diisononyl phthalate (DINP), dinonyl phthalate (DNP), diisodecyl phthalate (DIDP), ditridecyl phthalate (DTDP), diundecyl Phthalic acid plasticizers such as phthalate (DUP);
Trimellitic acid plasticizers such as tri-2-ethylhexyl trimellitate (TOTM), triisodecyl trimellitate (TIDTM), triisooctyl trimellitate (TIOTM), triisononyl trimellitate;
Pyromellitic plasticizers such as trioctyl pyromellitic acid (TOPM);
Adipic acid plasticizers such as di-2-ethylhexyl adipate (DOA), diisononyl adipate (DINA), diisodecyl adipate (DIDA);
Sebacic acid plasticizers such as di-2-ethylhexyl sebacate (DOS) and dibutyl sebacate (DBS);
Azelaic acid plasticizers such as di-2-ethylhexyl azelate (DOZ);
Phosphate plasticizers such as tricresyl phosphate (TCP) and tri-2-ethylhexyl phosphate (TOP); triethyl citrate, acetyl tri-n-butyl citrate, tri-n-butyl citrate, acetyl triethyl Citric acid plasticizers such as citrate and acetyltri- (2-ethylhexyl) citrate;
Alkyl sulfonic acid phenyl esters such as mezamol and mezamol II (both trade names, Bayer);
Cyclohexanedicarboxylic acid ester such as DINCH (trade name, BASF);
Etc. These may be used alone or in combination of two or more as required.

  Among these plasticizers, alkylsulfonic acid phenyl esters and cyclohexanedicarboxylic acid esters are preferable, and alkylsulfonic acid phenyl esters are particularly preferable because they are plasticizers having a high erasure rate and low stickiness.

  In the present invention, the liquid polymer can be used in combination with another ester plasticizer in a predetermined amount range to improve the migration resistance of the other plasticizer, and the surface is not sticky and has high erasability. It becomes possible to get erasure. Although its action is not clear, it is assumed that the ester plasticizer is incorporated into the liquid polymer chain and the bleeding out of the ester plasticizer is suppressed, thereby improving the migration resistance and stickiness. .

  The blending amount of the plasticizer in the eraser of the present invention is preferably 20 to 200 parts by mass in total with respect to 100 parts by mass of the base resin, and more preferably 50 to 180 parts by mass. If the blending amount of the plasticizer is less than 20 parts by mass, the erasing becomes hard and the elasticity is lowered and the erasability may also be lowered. If the amount exceeds 200 parts by mass, the erasing becomes too soft or the erasability is low. It tends to be difficult to use as an eraser.

  When the liquid polymer and other ester plasticizer are used in combination, the ratio of the liquid polymer in the total plasticizer needs to be 0.5% by mass or more and less than 20% by mass. When the ratio of the liquid polymer is less than 0.5% by mass, the effect of suppressing the migration of the ester plasticizer is not sufficient, and the anti-migrating migration resistance and stickiness improving effect are insufficient, which is not preferable. On the other hand, when the ratio of the liquid polymer exceeds 20% by mass, the liquid polymer itself tends to cause stickiness, which is not preferable. The ratio of the liquid polymer in the total plasticizer is more preferably 5% by mass to 18% by mass, and particularly preferably 5% by mass to 15% by mass.

  In the plastic eraser of the present invention, a filler can be blended in order to impart an appropriate hardness. As the filler, silica stone powder or limestone powder (heavy calcium carbonate) is generally used, and these inorganic powders are used after being finely divided so as not to damage the writing surface. In addition, diatomaceous earth, talc or shirasu powder, aerosil which is a fine powder of silicon oxide, inorganic and organic hollow particles, and the like can be used. Although the compounding quantity of these fillers changes with base-material resins, it is preferable that it is 30-250 mass parts with respect to 100 mass parts of base resin.

  Further, if necessary, a stabilizer is used in order to prevent high temperature deterioration due to molding of the base resin, particularly vinyl chloride resin. In order to improve the light stability, a light stabilizer such as an ultraviolet absorber can be blended. In addition, additives such as viscosity modifiers, lubricants, solvents, colorants, preservatives, antifungal agents, and fragrances can also be contained. The amount of these additives is not particularly limited as long as the effects of the present invention are not impaired.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely using an Example and a comparative example, this invention is not limited to a following example.

  The materials used in the following examples and comparative examples are shown in Table 1. In the following description, “part” means “part by mass” unless otherwise specified.

  How to determine SP value; M.M. The method of Coleman “Specific interaction and the miscibility of polymer blend” was used, and the liquid polyester used the Small formula.

  In the following examples and comparative examples, the erasing hardness, erasing rate, transferability, stickiness and strength obtained were measured or evaluated by the following methods.

[Hardness]
(1) C type (surface hardness); conformed to JIS S 6050: 2002 6.2. Using a hardness tester, the pressure surface was brought into contact with the surface of the test piece held horizontally so that the push needle of the tester was vertical, and the scale was immediately read.
(2) A type (internal hardness); using a type A durometer in accordance with JIS K 6253-3: 2006, as in the hardness measurement (C type) of JIS S 6050, The pressing surface was brought into contact with the surface so that the push needle of the testing machine was vertical, and the scale was immediately read as an integer.

[Erasing rate]
Conforms to JIS S 6050: 2002 6.4.
(1) The test piece was prepared by cutting the eraser into a plate having a thickness of 5 mm and finishing the tip portion in contact with the colored paper into an arc having a radius of 6 mm.
(2) Using a drawing machine, a colored paper is prepared using a pencil HB specified in JIS S 6006 and a high-quality paper having a basis weight of 90 g / m ² or more and a whiteness of 75% or more. The test piece is brought into contact with the test piece perpendicularly and at a right angle to the colored line, and a weight is placed on the test piece so that the sum of the weight of the weight and the holder is 0.5 kg. The colored part was brushed back and forth 4 times at a speed of min.
(3) Using a densitometer, the density of the non-colored part of the colored paper was set to 0, and the density of the colored part and the wear part was measured.
(4) The erasure rate was calculated by the following formula, and the average value of three times was obtained.
Erase rate (%) = (1− (density of wear part ÷ density of colored part)) × 100

[Migration resistance]
It conformed to JIS S 6050: 2002 6.3.
○: The paint does not adhere to the test piece.
X: The paint adheres to the test piece.

[Stickiness]
The eraser was placed on paraffin paper, placed in a 60 ± 2 ° C. incubator, taken out after 12 days, and evaluated by the stickiness when touched by the evaluator. There were 6 evaluators.
A: All felt that they were not sticky.
○: I felt that 1-2 people were sticky.
Δ: 3 to 4 people felt sticky.
X: I felt that 5 or more people were sticky.

[Strength (Folding resistance)]
When the eraser was held and folded with one hand, the number of times required to fold was measured.

(Examples 1-11, Comparative Examples 1-9)
After stirring the composition mix | blended by the compounding ratio (a number is a mass part) shown in Table 2, 3, under reduced pressure, it shape | molded at 100-150 degreeC, and produced plastic eraser. Tables 2 and 3 show the evaluation results for each eraser.

  From Table 2, by using a small amount of a liquid acrylic polymer in combination with an ester plasticizer, a non-sticky plastic eraser with no reduction in erase rate and excellent migration resistance was obtained. The stickiness improving effect was improved by using 5% by mass or more of the liquid acrylic polymer, and the effect became remarkable by using 10% by mass of the liquid acrylic polymer.

  Further, from Table 3, by using a small amount of liquid polyester in the ester plasticizer, a non-sticky plastic eraser with no reduction in erasure rate and excellent migration resistance was obtained. The stickiness improving effect was improved by using 5% by mass or more of liquid polyester.

  On the other hand, from Table 2 and Table 3, when 25 mass% or more of a liquid polymer is used in combination with an ester plasticizer (Comparative Examples 2, 3, 5, 7 to 9), a liquid polymer having an SP value of less than 8.75. When used in combination (Comparative Example 4), or when the liquid polymer used in combination was used in combination with an epoxy plasticizer (Comparative Example 6) even when 5% by mass, the result was sticky.

  The obtained eraser had a high erase rate, excellent migration resistance, and no stickiness on the surface. Further, the folding resistance is a value that does not cause a problem in practical use since the hardness is sufficient, and these had sufficient performance as an eraser.

Claims (4)

  In a plastic eraser containing a base resin, a plasticizer and a filler, as a plasticizer, an SP value of 8.75 or more, a liquid polymer at room temperature, and at least one ester plastic other than the liquid polymer A plastic eraser characterized in that the proportion of the liquid polymer in the total plasticizer is 0.5% by mass or more and less than 20% by mass.   The plastic eraser according to claim 1, wherein the liquid polymer is at least one selected from a liquid acrylic polymer and a liquid polyester.   The plastic eraser according to claim 2, wherein the weight average molecular weight (Mw) of the liquid acrylic polymer is 1,800 to 10,000. The plastic eraser according to claim 2, wherein the liquid polyester has a weight average molecular weight (Mw) of 800 to 4,000.