JPH0430536B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an inspection method that is effective for quality control of thermoplastic resins, particularly thermoplastic resins used as raw material resins for producing thin sheet or film molded products, blow molded products, etc. There are various types of thermoplastic resins, including vinyl chloride resin, polyethylene, polypropylene, and polyethylene terephthalate, which can be plasticized by heat and extruded, but in order to obtain high-quality products, the quality of these raw resins must be checked. Control is an extremely important point industrially, and preliminary quality inspection is required. To explain vinyl chloride resin in detail below, vinyl chloride resin is a general-purpose resin that is manufactured at low cost, and its sheet or film molded products are transparent,
Because of its excellent oxygen permeability resistance, it is used in large quantities for food packaging, clothing packaging, agricultural vinyl film, etc., but sheets and films that are consumed in large quantities like this are of high quality and are not commercially available. In order to have excellent value, it is desired that the initial discoloration, foreign matter, and fissures be as small as possible. A sheet or film with many initial discolorations, foreign substances, and hard eyes not only has an inferior appearance and low commercial value, but also has poor physical properties, and is disadvantageous because it may tear or crack during secondary processing of the sheet or film. occurs. Products with strong initial coloring often have poor thermal stability, and if there are many variations in initial coloring, this often results in fatal defects such as defective final products. In order to avoid such disadvantages, it is necessary to perform quality inspections on raw resins in advance as part of quality control, but no efficient, simple, and accurate inspection methods have been developed for thermoplastic resins such as vinyl chloride resins. Not yet. For example, in order to check the degree of initial coloration of vinyl chloride resins, etc., a sheet of transparent blended compound is kneaded in a roll and then press-molded into a plate of a certain thickness. For example, hunter's L (lightness), a (reddish),
B (yellowness) was used to control the color, but this method involved many work steps, required skill in particular for roll kneading, unavoidable individual errors, and took a considerable amount of time. This caused many problems in terms of manufacturing quality control. The present invention was completed as a result of intensive research into this technical problem, and consists of continuous extrusion molding of a thermoplastic resin to be tested into a transparent film with a thickness of 0.05 to 0.50 mm. After the object has passed through the cooling zone, it is passed continuously between the upper and lower reflectors, and visible light is emitted from the other end of the reflector to repeatedly pass through the film-like object, until the light reaches one end. receives light and measures tristimulus values,
The present invention relates to a thermoplastic resin quality inspection method characterized by determining a color control value from the results. The quality inspection method of the present invention is applied to various thermoplastic resins including vinyl chloride resins, and can also be applied for quality control purposes in large-scale equipment such as resin production processes. . The case of vinyl chloride resin will be explained below based on a dedicated quality inspection apparatus illustrated in the attached drawings. FIG. 1 shows a first embodiment of the compound, in which the vinyl chloride resin to be inspected is first made into a compound, then fed to an extruder 1 and continuously extruded into a film. Extruded film 7
is guided to the cooling roll 2, where it is cooled, and then
The initial coloring of the film 7 is identified while the film 7 is continuously run through a color measurement section 4, which will be described later, and tristimulus values X, Y, and Z are measured, and finally color management values such as L (lightness), a (reddish), b (yellowish), ΔL,
Obtain Δa and Δb. The film passes through a take-up roll 5 and is taken up by a take-up roll 6. The extruder 1 is one with a diameter of 30 mm or less, for example 20
A small size around mmφ is desirable because it allows efficient inspection with a relatively small amount of resin. This extruder is designed so that the screw compression ratio can be changed freely in order to check the film formability, and it is a breaker plate type in which a screen can be inserted to adjust the back pressure. 1, 2, 3 or 4, and whether a screen is required or not, from 42# to 325
# is used as needed. Furthermore, the cylinder C ₁ , cylinder C ₂ , head, and die have a temperature control mechanism, and the die is a coat hanger type, and by attaching an appropriate die spacer and adjusting the take-up speed appropriately, the coloring of the film can be adjusted. Obtain a film with a thickness of 0.05 to 0.50 mm, which is necessary for identifying and determining color control values. The screw rotation speed is preferably in the range of 10 to 100 rpm, particularly in the vicinity of 20 to 60 rpm in relation to the resin residence time. Furthermore, by attaching a torque meter and a resin pressure gauge, more accurate data for determining the moldability of the resin can be obtained. When disassembling and assembling the extruder 1, it is necessary to move the extruder 1 a little away from the normal installation location (the cooling roll 2, pulse transmitting roll 3, color measuring section 4, fixing eye, foreign object detector 9, etc. must be moved frequently). ), therefore, the first
As shown in the figure, it is convenient to install it on a rail so that it can be moved back and forth and also be adjustable in the vertical direction. The cooling roll 2 is generally of a water-cooled type. Since the film 7 extruded from the extruder is still hot, it needs to be cooled by the cooling roll 2, and it is recommended to install a water volume regulator or temperature regulator to ensure sufficient cooling and maintain a constant temperature. This makes it possible to eliminate uneven thickness, width, and surface unevenness. The color measurement section 4 is a mechanism also called a "non-contact dual-reflection transmission type" and is configured as follows. In other words, a film or sheet runs between two special reflective plates sandwiching it above and below, and visible light from a light source is projected from the other end of the two plates and repeatedly passes through the running film or sheet. After the light reaches the other end, the light is received by a light receiving section with a built-in light receiving element and the tristimulus values X, Y, Z are received.
The final color management values such as L, a,
Obtain b, ΔL, Δa, and Δb. FIG. 2 shows a second embodiment of the present invention, in which a color identification test for a film and a test for foreign matter or foreign matter in the film are performed at the same time.
This is an apparatus in which a gas laser beam scanning type detector 9 is further incorporated into the apparatus shown in FIG. This detector 9 is constructed on the following principle. That is, the gas laser beam (scanning laser beam) emitted from the laser passes through a lens system, then a rotating octagonal mirror, and then passes through the film 7.
reach the top. The light spot on the film is scanned in the width direction of the film by a high-speed rotating octagonal mirror, and the entire surface of the film is irradiated as the film travels. This scanning light passes through the film 7, enters the photoreceiver, is photoelectrically converted by a built-in photomultiplier tube, becomes an electrical signal, and is counted and displayed. The scanning laser beam is applied to the film 7 so as not to cause light absorption, heat generation, or optical changes.
It is desirable to use one with a wavelength of λ1000nm or less and an output of 10mW or less. For example, He-Ne (λ632.8nm output
A 5mW) gas laser is used, a half-color is used to distinguish between foreign objects and fisheyes, two light receivers are used, and a pulse transmitter (path transmitter roll 3) is used to adjust the time lag. Fish eyes can be detected in three stages: large, medium, and small, and each size range can also be measured freely. In FIG. 2, the detector 9 is arranged next to the color measuring section 4 when viewed in the film running direction, but the arrangement is not limited to this order, and the detector 9 can be arranged in the reverse order. It may be hot. Further, the pulse generating roll 3 may be subordinated to either the guide roller 8' or the take-up roll 5. The take-up roll 5 has the function of determining the traveling speed of the film 7 and adjusting the thickness of the film 7. That is, the thickness of the film 7 is determined by the take-up speed and the amount of extrusion. It is necessary to change the speeds of the cooling roll and take-up roll for hard and soft films, and therefore it is desirable to incorporate a speed ratio changing device for this purpose. The take-up roll 6 may be of any type as long as it can take up the film at an appropriate speed, and its mechanism is not limited. Although the quality inspection method according to the method of the present invention is widely applied to thermoplastic resins in general, it will be specifically explained in detail in the case of vinyl chloride resins. First, the vinyl chloride resin to be inspected is preliminarily made into a transparent vinyl chloride resin compound, but there are hard compound compounds and soft compound compounds, and in both cases, visible light and gas cannot be detected. Since it is required to transmit laser beams, it is desired that its transparency is 30 or less in Haze value, preferably 5 or less. Hard blended compounds are made by blending vinyl chloride resin with a heat stabilizer (for example, a tin stabilizer), and a small amount of lubricant such as epoxidized soybean oil, butyl stearate, or cetyl alcohol, and almost no plasticizer is blended. On the other hand, since soft compound compounds contain a considerable amount of plasticizer, it is necessary to maintain good dry flow properties of the compound in order to stabilize the amount supplied to the extruder, which is solved by incorporating an inorganic filler. be done. However, as mentioned above, due to the requirement for visible light and gas laser light transmission,
Carnosium carbonate or titanium dioxide cannot be used as fillers (each particle of the filler must be completely dispersed; any agglomeration will be counted as a fissure). According to the studies conducted by the present inventors, fine powder silica with an average particle diameter of 20 μm or less is extremely suitable as this filler. In other words, by using this filler, it is possible to maintain stable dry flow properties and to use gas lasers. It was confirmed that the detection and counting of the target foreign object, the fish eye, was carried out without any problems, without light being scattered.
Further, from the viewpoint of measuring the colorability of the vinyl chloride resin, it is naturally desirable that the amount of filler be small. From this point of view, the soft blended compound used is one in which the vinyl chloride resin to be tested is blended with a plasticizer, a heat stabilizer, and fine powdered silica with an average particle size of 20 μm or less. Examples of plasticizers include DOP, DOA, DBP, polyester plasticizers, epoxy plasticizers, and other commercially available plasticizers for vinyl chloride resin, and thermal stabilizers include Zn-Ca or Cd-Sn. Commercially available stabilizers for so-called vinyl chloride resins are used, respectively. Further, these hard or soft compounds may be blended with a lubricant as appropriate, such as higher alcohols, fatty acids, fatty acid esters, metal soaps, and the like. According to the present invention, the conventional method, that is, roll-kneading a vinyl chloride resin compound,
The sheets are stacked to a certain thickness and press-formed.
Furthermore, compared to the method of measuring the object using a colorimeter, the inspection time can be significantly reduced. Furthermore, since the present invention uses a non-contact dual-reflection-transmission type color measurement unit, the detection ability is greatly improved, and it exhibits excellent performance even for samples with only slight color differences. Moreover, this coloring property, foreign matter, and fissure eyes can be measured simultaneously within the extrusion time. On the other hand, conventionally, the time required to count fish eyes with the naked eye is 1 (compound 1).
kg, length 250m) (not including extrusion time), but apart from the approximately 25 minutes required for extrusion, the time required for identification, counting, and recording is virtually zero, and inspection This brings about the expected effects of time reduction and accurate analysis results. In the case of conventional naked-eye observation, there are inevitably individual differences, and even the same person performing the measurement cannot avoid the disadvantage that the judgment differs from day to day. However, according to the inspection method of the present invention, there is no error due to individual skill, and since multi-point measurements are performed and statistical processing is performed, extremely effective quality control is possible. Although the present invention has been explained above with a focus on vinyl chloride resins, it goes without saying that it is also effective for other thermoplastic resins as mentioned above, and also when a large extruder is used. is also valid. Next, examples of the present invention will be given. Example 1 Three vinyl chloride resins (manufactured by Shin-Etsu Chemical, trade name TK-1000) with an average degree of polymerization of 1050 (No. 1, No. 2, No.
The quality inspection of 3) was conducted on the following soft compound compound. Vinyl chloride resin 100 parts by weight DOP 40 〃 Ca-Zn stabilizer 3 〃 Thyroid 404 (*) 0.05 〃 (*) Product name manufactured by Fuji Davison Chemical Co., Ltd., fine powder silica Stir the above mixture with a Henschel mixer at the speed The mixture was mixed at 1800 rpm and a discharge temperature of 120°C to form a soft blended compound. This compound was supplied to the extruder of the apparatus shown in Figure 2 (see below), and film extrusion was performed under the following extrusion conditions. While running the film with a thickness of 0.15 mm and a width of 40 mm at a speed of 5 m/min, Initial coloring values, that is, Hunter's L, a, and b (L = brightness, a = reddish, b = yellowish) were measured using a non-contact double-sided multi-reflection color measurement unit with 45° incidence and 0° reception. When foreign matter and fish eyes were detected and measured using a He--Ne gas laser light scanning type detector, the results shown in Table 1 were obtained in a measurement time of 25 minutes. Extruder: Use a 20mmφ extruder,
L/D = 22, Screw CR = 2.0, Screw rotation speed 50 rpm, 2 pieces of Screw 80# Temperature conditions during extrusion: C ₁ = 155℃, C ₂ = 190℃,
H=170℃, D=205℃

[Table] Example 2 Three vinyl chloride resins with an average degree of polymerization of 700 (No. 4,
No. 5 and No. 6) were tested for quality as hard compound compounds as shown below. Vinyl chloride resin 100 parts by weight Sn stabilizer 2.5 〃 Epoxidized soybean oil 3 〃 Butyl stearate 1 〃 Cetyl alcohol 0.7 〃 The above mixture was mixed in a Henschel mixer at a stirring speed of 1800 rpm and a discharge temperature of 120°C to form a hard It was made into a compound. This compound was supplied to the extruder of the apparatus shown in Figure 2 (see below), and film extrusion was performed under the following extrusion conditions. While running the film with a thickness of 0.15 mm and a width of 40 mm at a speed of 4 m/min, The initial coloring values, that is, Hunter's L, a, b (L
= brightness, a = reddish, b = yellowish), and He-
When detecting and measuring foreign objects and fissures using a Ne gas laser optical scanning detector, we found that
The results shown in Table 2 were obtained after a measurement time of 10 minutes. Extruder: Use a 20mmφ extruder,
L/D=22, screw CR=1.0, screw rotation speed 20 rpm, temperature conditions during extrusion: C ₁ = 150℃, C ₂ = 175℃,
H=170℃, D=205℃

[Table] Example 3 Commercially available polypropylene (from companies A, B, and C, all in pellet form) with a melt index of 3 to 5 (g/10 minutes) was supplied to the apparatus shown in Figure 2. Then, the film was extruded under the following conditions, and while running the film with a thickness of 0.15 mm and a width of 40 mm at a speed of 4 m/min, it was extruded using the same non-contact dual-reflection-transmission color measurement unit as in Example 1. Initial coloration was measured, and foreign matter and fish eyes were also measured using a He-Ne gas laser scanning detector. The measurement time was 10 minutes, and the results shown in Table 3 below were obtained. In addition, the extruder used is one with a diameter of 20 mm, L/D=
22, Screw CR = 2, rotation speed 40 rpm, 2 screens 80 #, temperature conditions C ₁ = 170℃, C ₂ = 190℃,
H=180℃, D=190℃.

【table】 [Brief explanation of drawings]

FIGS. 1 and 2 are schematic diagrams of an apparatus for carrying out the method for inspecting the quality of thermoplastic resin according to the present invention. DESCRIPTION OF SYMBOLS 1... Extruder, 2... Cooling roll, 3... Pulse transmission roll, 4... Color measurement section, 5... Taking-up roll, 6... Winding roll, 7... Film, 8,
8'...Guide roller, 9...Gas laser light scanning type detector.

Claims (1)

[Claims] 1. The thermoplastic resin to be tested is continuously extruded into a transparent film with a thickness of 0.05 to 0.50 mm, and the resulting film is passed through a cooling zone, and then continuously run between the upper and lower reflectors. However, visible light is emitted from the other end of the reflector and passed through the film-like object repeatedly, and the light that reaches one end is received and tristimulus values are measured, and color management values are determined from the results. Quality inspection method for thermoplastic resin.