JP3522344B2 - Degradable protective film for helmet shields and goggle lenses - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective film which is used by being attached to or attached to a shield portion of a helmet and a lens portion of sports goggles.

[0002]

2. Description of the Related Art A protective film which is attached to or stuck to a shield portion or goggle lens portion of a helmet used in sports such as motorcycles, car races, ski competitions and other industrial fields is water,
When mud, oil, etc. adhere to obstruct the field of view, it is used to strip the field of view and secure the field of view. This protective film is usually used by peeling off a plurality of sheets so that they can be peeled off one by one. The properties required for this protective film are excellent in transparency, water resistance and oil resistance when used,
Also, it does not break when peeled off.

Therefore, the protective film used so far is made of polyethylene, polypropylene, polyethylene terephthalate or the like. In particular, those made of polyethylene terephthalate are generally used as a protective film because of their excellent transparency and high strength.

[0004]

However, when these plastic films are scattered in the natural environment, they do not decompose and cause pollution, or even if they are recovered and landfilled, they remain as they are. There are problems that the ground of the landfill is not stable and that the life of the landfill is shortened.

[0005]

Means for Solving the Problems The present invention solves the above problems, and after use / disposal, hydrolysis proceeds naturally in soil or water, leaving no original shape in soil, and then harmless by microorganisms. The present invention provides a protective film which becomes a decomposed product, has excellent transparency, and has strength, water resistance, and oil resistance that do not hinder normal use.

That is, the gist of the present invention is to use a film of polylactic acid-based polymer having a haze of 3% or less as polylactic acid
Multiple sheets of the film via an adhesive substance consisting of sesame
A decomposable protective film for helmet shields and goggle lenses, which is laminated in a peelable manner. Unlike a polyethylene terephthalate film or the like, such a film decomposes in a natural environment into a harmless decomposed product.

In the present invention, the film is made of a polylactic acid type polymer and has a plane orientation degree ΔP of 3.0 × 1.
0 ^-3 or more, and the difference between the heat of crystallization △ Hc generated by crystallization heat of crystal fusion △ Hm and during temperature rise when the temperature of the film (△ Hm- △ Hc) is 20 J / g or more The film is a sticky substance made of polylactic acid oligomer
A decomposable protective film for a helmet shield and a goggle lens, which is characterized in that a plurality of the films are laminated so as to be peelable via a quality . This film can be easily thinned and can be used more suitably in terms of strength and the like.

The present invention will be described in detail below. The polylactic acid-based polymer used in the present invention is polylactic acid or a copolymer of lactic acid and another hydroxycarboxylic acid, or a mixture thereof, and other polymer materials within a range that does not impair the effects of the present invention. May be mixed. Further, for the purpose of adjusting molding processability and film physical properties, a plasticizer, a lubricant,
It is also possible to add additives such as inorganic fillers and ultraviolet absorbers, and modifiers.

Lactic acid includes L-lactic acid and D-lactic acid, and other hydroxycarboxylic acids include glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid and 4-hydroxyvaleric acid. Typical examples include 6-hydroxycaproic acid and the like.

As these polymerization methods, any known method such as a condensation polymerization method and a ring-opening polymerization method can be adopted, and a small amount of a chain extender such as a diisocyanate compound for the purpose of increasing the molecular weight. , Epoxy compounds, acid anhydrides, etc. may be used. The weight average molecular weight of the polymer is preferably 50,000 to 1,000,000, and practical physical properties are hardly expressed below this range.
If it exceeds, the melt viscosity becomes too high and the moldability becomes poor.

The protective film of the present invention can be obtained from this polylactic acid polymer by melt-molding the polylactic acid polymer into a sheet and rapidly cooling it to obtain a transparent film. Since the protective film may be used by laminating a plurality of sheets, one film has a high transparency,
Specifically, the haze defined by JIS-K-7105 is preferably 3% or less, and more preferably 2% or less. Polylactic acid-based polymer is more transparent than other currently known degradable resins, but in order to obtain preferable transparency as a protective film, the film should be made as thin as possible,
It is important to prevent spherulite formation by quenching during melt molding. It is also effective to suppress the addition of additives that impair transparency, especially solid additives.

Particularly preferably, it is practical that the polylactic acid polymer is melt-formed into a sheet and rapidly cooled to obtain an unstretched sheet, which is then subjected to a stretching treatment and a heat treatment. Explaining the film forming conditions of the unstretched sheet, the polylactic acid-based polymer is sufficiently dried to remove water, and then melted by an extruder. Since the melting temperature changes depending on the composition, it is preferable to appropriately select the melting temperature. Actually 1
A temperature range of 40 to 230 ° C. is usually chosen.

The polymer melt-formed into a sheet is preferably brought into contact with a rotating casting drum (cooling drum) to be rapidly cooled. The temperature of the casting drum is preferably 50 ° C. or lower. If it is higher than this, the polymer sticks to the casting drum and cannot be removed. In addition, crystallization is promoted, spherulites develop, and stretching becomes difficult. Therefore, it is preferable to set the temperature within the above temperature range and quench the material to make it substantially amorphous.

The stretching method may be either uniaxial stretching, sequential biaxial stretching or simultaneous biaxial stretching, but biaxial stretching is desirable because it is necessary to improve the physical properties in both the longitudinal and transverse directions for the purpose of use. The stretching ratio of the sheet in the present invention is in the range of 1.5 to 5 times in each of the longitudinal direction and the transverse direction,
The stretching temperature is appropriately selected in the range of 50 ° C. to 90 ° C., and the degree of plane orientation ΔP, which is 1.0 × 10 ⁻³ or less in the non-oriented sheet, is increased to 3.0 × 10 ⁻³ or more, so that even a thin wall can be obtained. You can get a tough film.

ΔP represents the degree of orientation in the plane direction with respect to the thickness direction of the film, and is usually calculated by the following formula by measuring the refractive index in the directions of three orthogonal axes. ΔP = {(γ + β) / 2} -α (α <β <γ) where γ and β are biaxial refractive indexes orthogonal to the film surface, and α is a refractive index in the film thickness direction.

Although ΔP depends on the crystallinity and the crystal orientation, it largely depends on the molecular orientation in the film plane. That is, the increase of ΔP is achieved by increasing the molecular orientation in the plane of the film, particularly in the film flow direction and / or the direction perpendicular thereto, thereby increasing the strength of the film and improving the brittleness. As a method for increasing ΔP, in addition to all known film stretching methods, a molecular orientation method using an electric field or a magnetic field can be adopted.

The upper limit of ΔP is practically about 30 × 10 ^-3 , and if ΔP is made higher than this, there is a disadvantage that stretching becomes unstable or impossible. By setting ΔP to be 3.0 × 10 ⁻³ or more as described above, the strength is remarkably improved, and the embrittlement and whitening mainly caused by spherulite growth observed in the case of the non-oriented sheet are prevented. be able to.

On the other hand, however, the thermal dimensional stability of the film becomes poor, and the film shrinks during the hot summer months, making it unsuitable as a protective film that is often used outdoors. Therefore, it is important to be able to return to its original shape without shrinking in an atmosphere at a temperature slightly higher than room temperature, that is, at a temperature of about 50 ° C. or higher.

In order to obtain a practical thermal dimensional stability in a polylactic acid type film having a ΔP of 3.0 × 10 ⁻³ or more, the (ΔHm-ΔHc) of the film should be controlled to 20 J / g or more. is important. That is, (ΔHm-ΔH
If c) is less than 20 J / g, the thermal dimensional stability of the film is poor and it is not suitable for practical use as a protective film used outdoors, but if it is 20 J / g or more, the thermal dimensional stability is It is good and has no problems in practical use. ΔHm, Δ
Hc is the differential scanning calorimetry (DS) of the film sample.
C), and ΔHm is the heating rate of 10 ° C.
It is the amount of heat required to melt all the crystals when the temperature is raised at / min, and is calculated from the area of the endothermic peak due to crystal melting that appears near the crystal melting point of the polymer. Also, ΔHc is
It can be determined from the area of the exothermic peak generated during crystallization that occurs during the temperature rising process.

ΔHm mainly depends on the crystallinity of the polymer itself, and takes a large value in a polymer having high crystallinity. By the way, for homo-L-lactic acid polymer without copolymer,
It becomes 0 J / g. ΔHc is an index relating to the crystallinity of the film at that time with respect to the crystallinity of the polymer,
When ΔHc is large, it means that the crystallization of the film proceeds during the temperature rising process, that is, the crystallinity of the film was relatively low based on the crystallinity of the polymer. On the other hand, when ΔHc is small, it means that the crystallinity of the film was relatively high based on the crystallinity of the polymer.

That is, one direction for increasing (ΔHm-ΔHc) is to use a polymer having high crystallinity as a raw material.
To make a film with a relatively high degree of crystallinity. The crystallinity of the film depends to a large extent on the composition of the polymer, but is also greatly influenced by the processing conditions of the film. In order to increase the crystallinity of the film in the molding process step, particularly in the tenter method biaxial stretching, it is useful to increase the stretching ratio to promote oriented crystallization, and to perform heat treatment after stretching in an atmosphere at a crystallization temperature or higher.

The heat treatment temperature is effectively higher than the crystallization temperature of the film, but the crystallization temperature of the film tends to decrease as ΔP increases, and in the case of the present invention, 90 ° C to 160 ° C. Thermal dimensional stability can be imparted by performing heat treatment for 5 seconds or more in the range of ° C.

The thus obtained film is usually used by peeling a plurality of sheets using an adhesive substance such as polylactic acid oligomer. At that time, it is usual that the peripheral portion of the film is not adhered and is easily peeled off. The laminated film can be directly attached to a hermetic shield or goggles lens, or can be attached to a frame provided around the shield for use.
The thickness of one film can be generally about 20 to 150 μm, and from this point as well, a stretched film that is easily thinned is preferable.

Examples will be shown below, but the present invention is not limited thereto. The measured values shown in the examples were measured and calculated under the following conditions. (1) Immersion in water degradability test The test was performed according to the immersion method in water in the field test of the biodegradable plastics research group. That is, the film was cut into 120 mm × 30 mm, and it was sandwiched in the center of three stainless steel sample holders. A window with the same shape as the film sample is opened in the center of the sample holder, and two stainless steel wire nets (40 mesh) are chewed so that the film does not flow out as it is and is in good contact with water. I chose

After soaking in fresh water for 3 months in winter, the weight average molecular weight retention, appearance and touch of the film were examined. The weight average molecular weight was Chromatopack C-R4A GPC manufactured by Shimadzu Corporation, and the film sample was dissolved in chloroform to prepare a concentration of about 0.5 (w / v)%, and the flow rate was 1.0 m /
Min, column temperature was measured at 40 ° C., and polystyrene conversion was performed. The weight average molecular weight retention is (sample weight average molecular weight before immersion)-(sample weight average molecular weight after immersion)
Was divided by the weight average molecular weight of the sample before soaking and expressed in%.

(2) ΔP The refractive index (α, β,
γ) was measured and calculated by the following formula. ΔP = {(γ + β) / 2} −α (α <β <γ) γ: Maximum refractive index in the film plane β: Refractive index in the in-plane direction of the film orthogonal thereto α: Refractive index in the film thickness direction (3 ) ΔHm-ΔHc Using DSC-7 manufactured by Perkin Elmer, based on JIS-K7122, the heat of crystal fusion ΔHm and the heat of crystallization ΔHc were calculated from the thermogram when the temperature was raised at a heating rate of 10 ° C./min. Obtained and calculated.

(4) Breaking strength Using a Tensilon II type machine manufactured by Toyo Seiki Co., Ltd., JIS-K7
It was measured based on 127. The measurement temperature is 23 ° C. and the pulling speed is 100 mm / min. MD indicates the flow direction of the film, and TD indicates the direction orthogonal to the flow of the film. (5) Hydroshock Impact Strength Impact resistance was measured using a high-speed impact tester HTM-1 (Hydroshot) manufactured by Shimadzu Corporation. 10 films
It was cut out to a size of 0 mm × 100 mm, fixed with a clamp, and a shock was applied to the center of the film by dropping, and the energy was read. The measurement temperature was 23 ° C., and the dropping speed was 3 m / sec.

(6) Thermal Dimensional Stability A film sample was cut into a size of 100 mm × 100 mm, immersed in a hot water bath at 80 ° C. for 10 seconds, and then the vertical and horizontal dimensions were measured. It was used as an index of dimensional stability. (7) A heat-resistant film sample was cut into a size of 100 mm × 100 mm and left in a constant temperature bath at 60 ° C. for 7 days, and the appearance (transparency) and shrinkability were examined.

(8) Film Strength at Peeling A film sample was cut into 100 mm × 100 mm, and a polylactic acid oligomer as an adhesive was applied very thinly in the center of the film sample, about 80 mm × 80 mm, and a film sample of the same type was used for MD The TDs were aligned and pasted together and left at room temperature. After 5 hours, the film was peeled off from one corner by hand and examined for film breakage. (9) Haze Measured according to JIS-K7105.

Examples 1 to 6 Poly-L-lactic acid having a weight average molecular weight of 100,000 was heated at 180 ° C. in a 30 mmφ single screw extruder.
Then, it was extruded from a T-die and rapidly cooled with a casting drum to obtain an unstretched sheet. Then, lengthwise roll stretching and widthwise tenter stretching were carried out under the conditions shown in Table 1, followed by heat treatment in the tenter to obtain films having thicknesses shown in Table 1. The film flow speed was 3 m / min, and the passing time through each stretching / heat treatment zone was about 20 seconds. The evaluation results for each film are shown in Tables 1, 2, and 3.

Comparative Example 1 A commercially available biaxially stretched polyethylene terephthalate film (thickness: 50 μm) was subjected to an immersion test in water. The results are shown in Table 2.

[0032]

[Table 1]

[Table 2]

[Table 3]

As shown in the results in Table 2, the polyethylene terephthalate film of Comparative Example showed almost no decomposability in water, whereas the polylactic acid film of Example showed decomposability. Further, as a result of evaluating the strength and the like of the polylactic acid films of Examples, as shown in Table 3, when ΔP is 3.0 × 10 ⁻³ or more, (ΔHm−ΔHc) is 20 J / g.
The films of Examples 4 to 6 described above were particularly suitable in terms of strength, heat resistance and the like.

[0034]

According to the present invention, it decomposes in a natural environment,
A degradable protective film for a hermetic shield and a goggle lens, which is made of a polylactic acid-based polymer having excellent transparency, can be obtained. Especially, the plane orientation degree ΔP is 3.0 × 10 ^-3
And the heat of crystal fusion ΔHm when the film is heated and the heat of crystallization Δ generated by crystallization during the temperature rise.
The film having a difference from Hc (ΔHm−ΔHc) of 20 J / g or more is excellent in various practically required properties such as strength and heat resistance.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jun Takagi 5-8 Mitsuya-cho, Nagahama-shi, Shiga Mitsubishi Jushi Co., Ltd. Nagahama factory (72) Inventor Shigenori Terada 5-8 Mitsuya-cho, Nagahama-shi, Shiga Mitsubishi Resin Co., Ltd. Nagahama Plant (56) References JP-A-64-68259 (JP, A) JP-A-6-23836 (JP, A) Special Tables 5-508819 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) A61F 9/02 A42B 3/24 G02C 11/00-11/08

Claims (2)

(57) [Claims] 1. A sticky substance comprising a polylactic acid polymer and a film having a haze of 3% or less and a polylactic acid oligomer.
A decomposable protective film for a helmet shield and a goggle lens, which is obtained by laminating a plurality of the films so that they can be separated from each other . 2. A film made of a polylactic acid-based polymer, having a degree of plane orientation ΔP of 3.0 × 10 ⁻³ or more, and a heat of crystal fusion ΔHm and a temperature rise when the film is heated. Difference from the heat of crystallization ΔHc generated by crystallization inside (△
Hm- △ Hc) is the 20J / g or more of the film, Po
Through the adhesive substance consisting of polylactic acid oligomer,
A decomposable protective film for helmet shields and goggle lenses, which is made by stacking multiple layers so that they can be peeled off .