BUSINESS SEGMENT INFORMATION - Geographic Area (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Segment Reporting Information [Line Items]
Net sales by geographic area:	$ 994.8	$ 1,016.7
Cost of products sold	792.2	817.3
Selling, general and administrative expenses	146.1	160.2
Acquisition and integration related costs	0.7	2.8
Restructuring charges and other	14.2	3.3
Non-cash asset impairment charges	0.2	0.3
(Gain) loss on disposal of properties, plants and equipment, net	(215.7)	(2.4)
Loss on disposal of businesses, net	0.5	1.1
Operating profit	256.6	34.1
Customized Polymer Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	305.1	294.4
Cost of products sold	247.3	235.8
Selling, general and administrative expenses	51.8	53.2
Acquisition and integration related costs	0.7	2.8
Restructuring charges and other	2.3	1.1
Non-cash asset impairment charges	0.0	0.3
(Gain) loss on disposal of properties, plants and equipment, net	0.0	0.1
Loss on disposal of businesses, net	0.5	0.0
Operating profit	2.5	1.1
Durable Metal Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	354.8	355.9
Cost of products sold	284.1	286.9
Selling, general and administrative expenses	34.1	39.5
Acquisition and integration related costs	0.0	0.0
Restructuring charges and other	3.8	0.7
Non-cash asset impairment charges	0.0	0.0
(Gain) loss on disposal of properties, plants and equipment, net	(0.1)	(2.8)
Loss on disposal of businesses, net	0.0	1.1
Operating profit	32.9	30.5
Sustainable Fiber Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	311.9	344.0
Cost of products sold	246.7	279.7
Selling, general and administrative expenses	54.1	61.5
Acquisition and integration related costs	0.0	0.0
Restructuring charges and other	8.0	1.4
Non-cash asset impairment charges	0.2	0.0
(Gain) loss on disposal of properties, plants and equipment, net	(215.6)	0.3
Loss on disposal of businesses, net	0.0	0.0
Operating profit	218.5	1.1
Innovative Closure Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	23.0	22.4
Cost of products sold	14.1	14.9
Selling, general and administrative expenses	6.1	6.0
Acquisition and integration related costs	0.0	0.0
Restructuring charges and other	0.1	0.1
Non-cash asset impairment charges	0.0	0.0
(Gain) loss on disposal of properties, plants and equipment, net	0.0	0.0
Loss on disposal of businesses, net	0.0	0.0
Operating profit	2.7	1.4
UNITED STATES
Segment Reporting Information [Line Items]
Net sales by geographic area:	493.8	523.8
UNITED STATES | Customized Polymer Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	124.8	122.2
UNITED STATES | Durable Metal Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	62.5	64.0
UNITED STATES | Sustainable Fiber Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	300.4	331.4
UNITED STATES | Innovative Closure Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	6.1	6.2
EMEA
Segment Reporting Information [Line Items]
Net sales by geographic area:	346.9	329.2
EMEA | Customized Polymer Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	127.7	115.9
EMEA | Durable Metal Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	209.4	202.7
EMEA | Sustainable Fiber Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	0.2	0.2
EMEA | Innovative Closure Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	9.6	10.4
Asia Pacific And Other Americas
Segment Reporting Information [Line Items]
Net sales by geographic area:	154.1	163.7
Asia Pacific And Other Americas | Customized Polymer Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	52.6	56.3
Asia Pacific And Other Americas | Durable Metal Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	82.9	89.2
Asia Pacific And Other Americas | Sustainable Fiber Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	11.3	12.4
Asia Pacific And Other Americas | Innovative Closure Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	$ 7.3	$ 5.8